How to switch phone providers without downtime: a number porting guide

How long does it take to port a business number?

A simple single-line port must complete within one business day under FCC rules. A multi-line business port typically takes 5 to 10 business days from an accepted request, because it is a non-simple port and the carriers coordinate a cutover date.

The regulation is 47 CFR 52.35. Paragraph (a) requires all carriers that port numbers to complete a simple wireline-to-wireline or simple intermodal port within one business day unless the new provider or the customer asks for longer. Intermodal ports include ports involving interconnected VoIP service (52.35(e)(2)), so a move from a traditional landline to a cloud phone system is covered. A complete request received between 8 a.m. and 1 p.m. local time qualifies for activation at midnight the same day; later requests count as received the next business day. Paragraph (d) gives non-simple ports four business days unless the customer or new provider asks for longer.

The FCC’s consumer guide describes simple ports as those that generally do not involve more than one line or more complex adjustments to telephone switching equipment. The FCC’s 2010 order setting the one-day interval defined a simple port more precisely (FCC 10-85). It involves an account for a single line, no unbundled network elements, no complex switch translations such as hunt groups, and no reseller.

Most practice phone accounts are non-simple. A main number with a fax line, a back line and a hunt group is a multi-line account with switch translations. The four-business-day interval in 52.35(d) applies to the carrier’s processing once the request is accepted. The new provider and the customer commonly ask for a longer window to schedule the cutover, verify the account details and ship hardware. That is why business providers quote 5 to 10 business days rather than four. ZentryVoice states 5–10 business days for business lines.

Three things stretch the timeline beyond that range. A rejected request must be corrected and resubmitted. A toll-free number moves through a different process. A wireless number involves the wireless carrier’s own port-out controls. The delay table below covers each.

What documents does a port need?

A port needs two things to match: a signed Letter of Authorization from the practice and the current carrier’s Customer Service Record. Almost every rejection is a mismatch between them.

The Letter of Authorization (LOA). The new provider supplies the form. It names the practice as it appears on the current carrier’s account and lists every telephone number to be ported. It gives the service address and account number, and is signed and dated by an authorized person. The signer should be the account holder of record or an officer the carrier will recognize. An LOA signed by an office manager when the account is in the practice owner’s name is a common rejection.

The Customer Service Record (CSR). This is the current carrier’s own record of the account: legal name, service address, billing telephone number (BTN), account number and the list of numbers and features on the account. The practice can request it from the current carrier, or the new provider can request it with the LOA. A recent bill carries most of the same information and is the usual substitute.

The port request the new provider submits is called a Local Service Request (LSR) in the wireline process. It must match the CSR field by field. “Smith Family Dental” on the LOA and “Smith Family Dental PLLC” on the CSR can be enough to reject. “Suite 200” versus “Ste 200” can be enough. The fix is boring: copy the CSR exactly.

A port-out PIN or account passcode, where the current carrier uses one. See the section on PINs below.

A list of what each number does. Main line, fax, back line, after-hours, a number printed on forms. The new provider needs this to build the call flow before cutover, so that each number rings where it did on the morning after.

What are the steps, in order?

A business port follows nine steps. The practice does the first three; the providers do most of the rest.

1. Inventory the numbers. List every number the practice owns, what it does and whether it is on the main carrier account or a separate one. Fax lines, alarm lines and a forgotten second account are the usual surprises.
2. Pull the CSR or latest bill. Confirm the legal name, service address, account number and BTN exactly as the current carrier holds them. Fix anything out of date with the current carrier first, because a port request against stale records will be rejected.
3. Sign the LOA. Have the account holder of record sign the new provider’s LOA listing every number from step 1. Attach the bill or CSR and the port-out PIN if one exists.
4. Start service on the new system while the old one stays live. Set up extensions, voicemail greetings, call flows and texting registration on the new system using temporary numbers. Staff learn the system with nothing at stake.
5. Forward the existing number to the new system. Call forwarding at the old carrier, or a parallel ring, sends inbound calls to the new system from day one. Patients and clients notice nothing.
6. The new provider submits the port request. The current carrier validates it against the CSR and either accepts it with a Firm Order Commitment (FOC) date or rejects it with a reason code. Rejections are corrected and resubmitted; each round costs a few business days.
7. Confirm the FOC date and time. Cutover is usually scheduled for a quiet window. The new provider confirms call flows are built for each number and that 911 dispatchable location is set for each extension under Kari’s Law and RAY BAUM’s Act.
8. Cutover. On the FOC date the number moves to the new carrier’s routing. Inbound calls start arriving directly rather than through forwarding. Test each number inbound and outbound, test fax, test a text to the main number, and test 911 location data per your provider’s procedure.
9. Cancel the old service after confirmation. Only once every number is confirmed live on the new system. The FCC’s guide warns against cancelling the old service first, because a cancelled account can release the number before the port completes. Review the old contract for early-termination fees and outstanding balances; the old provider cannot refuse the port over them, but it can bill them.

Steps 4 and 5 are what make the switch downtime-free. The port is a background process while the office works on the new system.

How do you avoid downtime during the port?

Downtime during a port comes from three mistakes, and all three are avoidable: cancelling the old service early, cutting over without forwarding, and leaving call flows unbuilt on the new system.

Keep the old service active until the port confirms. The number belongs to the old carrier until the FOC date. A cancelled account can orphan the number, and recovering an orphaned number can take weeks. The FCC’s guide tells customers not to cancel before the new service is in place.

Forward from day one. With the old carrier forwarding to a temporary number on the new system, every inbound call lands on the new extensions, voicemail and timeline immediately. Outbound calls can show the practice’s existing number as caller ID on most platforms during the forwarding period, so patients see the number they know. Texting from the main number has to wait until the number ports and 10DLC registration completes, so plan patient texting for after cutover or register a temporary number.

Build the call flow before cutover. Ring groups, after-hours routing, voicemail boxes, fax-to-timeline and the 911 dispatchable location for each extension should be live and tested on the temporary numbers. On the FOC date, the ported numbers are pointed at flows that already work.

Run in parallel for a few days. Keep the old carrier’s forwarding in place through the FOC date and a few days after. If a number fails to port on schedule, forwarding still carries calls.

Schedule cutover for a quiet window. Early morning or after hours on a weekday, when the carrier’s porting desk is open to fix issues and patient call volume is low. Avoid Fridays, because a problem may sit until Monday.

On ZentryVoice, soft extensions on desktop and mobile are live during the 30-day trial, desk phones arrive pre-provisioned in 2–3 business days, and the existing number forwards to the new system from day one while the port runs. The unified communications guide describes what the office gets on the other side.

What can delay a port?

Most delays trace to the account record, not the carriers. The table lists the common causes, the usual fix and the time each one adds.

The common thread is preparation. A port that is rejected twice for paperwork takes three weeks; the same port submitted clean takes a week. The time between accepted request and FOC is the carriers’ interval; the time before that is the practice’s.

What is a port-out PIN, and when do you need one?

A port-out PIN is a code the current carrier requires before releasing a number to another provider. It exists to stop someone else from stealing the number, and it is now required practice for wireless carriers under FCC rules.

In November 2023 the FCC adopted rules under 47 CFR parts 52 and 64 for wireless providers. They must use secure methods of authenticating a customer before redirecting a number to a new device or carrier, and must notify customers of SIM-change and port-out requests. Wireless carriers implement this with a number transfer PIN that the customer generates in the account and gives to the new provider. A business that ports a wireless number into its phone system needs that PIN on the port request.

Wireline and VoIP providers are not covered by the 2023 wireless rules, but many use an account passcode or PIN for the same purpose, and some let customers freeze the account against ports. The practice should ask the current provider two questions before submitting: is a PIN or passcode required to port out, and is there a freeze on the account. Both are common reasons for a rejection that looks like a mismatch.

The same mechanism protects the practice after the switch. Ask the new provider how it authenticates a port-out request against your account, who in the practice is authorized to approve one, and how you will be notified. A practice’s main number is an asset that patients and referrers have memorized; it should be as hard to steal as the bank account.

How ZentryVoice handles this

ZentryVoice runs the port on the practice’s behalf and keeps the office working throughout.

• Timeline: ZentryVoice states 5–10 business days for business lines from an accepted request, with a scheduled FOC date confirmed before cutover.
• Paperwork: the LOA is generated in the signup wizard from the numbers the practice lists; the practice attaches a recent bill or CSR and any port-out PIN. ZentryVoice checks the request against the CSR before submitting it, which removes the most common rejection.
• No downtime: soft extensions on desktop, iOS, Android and web are live during the 30-day trial, the existing number forwards to the new system from day one, and desk phones arrive pre-provisioned in 2–3 business days.
• 911: each extension carries a validated dispatchable location under Kari’s Law and RAY BAUM’s Act before the ported numbers go live.
• Cost: no porting fee. Seats are $20 per user per month, month-to-month, and the pricing page computes the full quote.
• Leaving: numbers can be ported out at any time; there is no annual term and no early-termination fee.

The hidden costs guide covers porting fees and early-termination fees at other providers, and the vertical guides cover compliance for each kind of practice.