Because FCC rules let you keep your number when you switch carriers, a US cell phone number does not tell you who runs the line today. To transfer yours, sign up with the new carrier first, give it your number, account number, ZIP code and passcode, and let it ask your old carrier to release the number. Do not cancel the old line yourself: the FCC advises keeping the old service active until the new one starts. A simple port is meant to finish within 1 business day (47 CFR 52.35).
What a port is under US rules
Local number portability lets you move your number to another provider in the same area. The FCC’s consumer guide to porting says it works between wireless, wireline and VoIP providers. Wireless carriers have had to offer it since 2003. The FCC adds that moving to a new area may prevent you from keeping your number, so check with the carrier before you relocate.
When you switch, your new carrier sends the request to the old one through the numbering administrator. The old carrier checks it against the details you supplied, and only then do the two carriers coordinate the move.
Gather four details, then let the new carrier start the port
The FCC limits what the old carrier may ask the new one for in a simple port. The customer-supplied fields are the 10-digit number, the account number, the 5-digit ZIP code and a passcode, if you set one (47 CFR 52.36). The FCC wireless FAQ also suggests bringing a recent wireless bill, because it shows your name and address as the carrier has them on file.
- Keep your current service active. Do not cancel it.
- Find your account number and ZIP code from the old carrier, plus any passcode on the account.
- Give the new carrier your 10-digit number and those details, and ask to port the number in.
- Wait for the new service to start, then check that calls and texts reach you.
The FCC wireless FAQ says the new carrier confirms your identity and files the request. Ask the new carrier how the port will affect 911: during the switch, calls should connect, but the operator may not be able to call you back if the call drops.
The FCC describes port-out fraud as a scammer opening an account with another provider and moving your number to it. A customer-assigned passcode on your account must be provided before a port can proceed, so ask your carrier whether you can add one.
How long a port takes
The federal interval depends on the type of port. Business days run Monday to Friday, excluding the old carrier’s own holidays. A complete request received by 1 p.m. local time counts as received that day, while a later one counts as received at 8 a.m. the next business day (47 CFR 52.35).
| Type of port | Time | Basis |
|---|---|---|
| Wireless to wireless | About 2.5 hours, an industry target | FCC wireless FAQ (not mandated) |
| Simple landline to landline | 1 business day | 47 CFR 52.35(a) |
| Simple port between landline, wireless or VoIP | 1 business day | 47 CFR 52.35(a) |
| Non-simple port | 4 business days, unless a longer period is requested | 47 CFR 52.35(d) |
You or the new carrier can request a later date. The text of section 52.35 defines intermodal ports as those between wireline and wireless, or involving interconnected VoIP, and sets the same 1-day interval for the simple ones.
Why a port gets refused or stalls
An unpaid bill is not a valid reason. Once you have requested service from a new carrier, the old one may not delay or refuse the port because you owe a balance or an early termination fee. You still owe both, though, so read your contract first.
Mismatched details can stall a port, since the old carrier validates the request against its records. Check the account number, ZIP code and passcode, then ask the new carrier to resubmit. The FCC also notes that some rural wireline providers have waivers, in which case your state public utilities commission can help.
Carriers can charge a fee when a number is ported, and the FCC does not set the amount, although charges must be just and reasonable. Ask the new carrier whether it will cover the fee.
If the port still fails, file a complaint at consumercomplaints.fcc.gov.
Business lines: VoIP, landline and toll-free numbers
Interconnected VoIP providers must facilitate valid port requests, and they cannot use unreasonable delays or procedures to block one (47 CFR 52.34). Carriers owe the same duty when a number is moving to or from a VoIP provider. A company moving a line to a VoIP phone system is covered, and the 1-day or 4-day interval above applies depending on how simple the port is.
Toll-free numbers follow another path. The FCC explains that a subscriber ports a toll-free number by moving it to a new Responsible Organization (RespOrg). If the current RespOrg refuses, the subscriber can ask the TFNA Help Desk to make the change.
Ported numbers and SMS: finding the real network
A contact file built before a port often still shows the old carrier next to the number. Sending platforms route each message to a specific network, so stale data can complicate SMS routing and hurt deliverability. The filters carriers apply weigh on deliverability too.
HLR Lookup queries the network for each number and returns its line status and current carrier, MCC and MNC included. The service identifies both the original and the current network, which shows whether a line changed network while keeping its number. HLR is only one of the steps to validate a mobile phone number before a send.
The check gives the state of the number at the moment of the query. A number can be ported the next day, so keeping a clean customer file means repeating the check, with the date of the last check next to each line.
Run a sample of your database through HLR Lookup before your next SMS campaign and compare the network you get with the one stored in your file.
