Skip to main content
CallTower Solutions Center

CallTower - Porting Number Tips


Local Number Portability (LNP): this is the process of taking your existing phone numbers with you when you move or change carrier or service provider. Sounds simple enough, right? For example, a company moves, or they get a new phone system, so they tell the new carrier what their numbers are, the new carrier adds them to the new system, and they're done. 

Well, no. Unfortunately, it’s almost never that simple. There are a series of often baffling and, on the surface, appears to be inconsistent rules and regulations that need to be carefully navigated in order to port your numbers successfully.

Why is it so difficult?
The truth is, some of these rules are here to protect you from the current carrier, who may not be thrilled that you are taking your service elsewhere. But there are also rules to protect the carriers from their customers when someone is trying to slip out of a contract or an unpaid bill.

But most of these rules exist to protect you and your phone number and to verify your identity and authority to own and carry these numbers with you. These are federal regulations in place to protect the security of your phone calls and numbers.

Combined, porting rules can be confusing. While a carrier can reject a port for various reasons, generally, there are only a few common errors that can stall the your LNP request. This article will inform you about a few and discuss how CallTower can help navigate them.


First, a few acronyms. 

  • LNP – Local Number Portability. This is the act of porting numbers from one service provider or carrier to a new service provider or carrier. 
  • BTN – Billing Telephone Number. This is essentially the account number of the business at the losing carrier. Often it is the same as the “main” number for the business, but not always. In some cases, a customer might not even know what it is. 
  • LOA – Letter of Authorization. This is the form a customer must fill out and sign that declares their intent to port the numbers from the current carrier to the new carrier. All the information on this form must exactly match the information on the old account. 
  • CSR– Customer Service Record. This is the official billing record for the customer's account at the old carrier, which includes the BTN, the account number, the service address, the numbers assigned to the account, and of course, the account owner. All of this information must exactly match the information on the LOA for a new account to port in the customer's old numbers successfully.
  • CPNI – Customer Proprietary Network Information. This is the information that a carrier will maintain on the customer's account. It includes information such as the number list, optional services subscribed to, current charges, directory assistance charges, usage data, and calling patterns. In general, anything that appears on a phone bill is protected as CPNI.
  • LSP – Losing Service Provider or the carrier from which customers are porting out their numbers.
  • FOA-  Firm Order Commitment. This is acknowledged by the winning company of receipt of an access service request from the customer and commitment by the new company to the service date.

Process Overview

All LNP (Local number portability) requests start with an LOA (Letter of Authorization) that you will submit to CallTower. The LOA (Letter of Authorization) authorizes CallTower to act on your behalf in submitting the LNP (Local number portability) request to the LSP (Losing Service Provider). However, the LOA (Letter of Authorization) DOES NOT grant or give CallTower authorization to access or modify your account with the LSP (Losing Service Provider). Only you are authorized to do so, and only you can access your account and CPNI data at the LSP (Losing Service Provider). All carriers must certify annually that they have secured and have procedures in place to safeguard a customer’s CPNI data. Carriers can face stiff fines if it is shown that they are not sufficiently protecting their customer’s CPNI. This is why CallTower cannot request your account information from an LSP (Losing Service Provider). Please do not ask CallTower to do this for you; unfortunately, CallTower must always say no.

Common Errors

Address and Zip Code Mismatch

This is the most common rejection. But the name of this error does not always reflect the underlying issue; This means the address on the LOA that you submitted does not match the address on the account with your current carrier.

  • How Do You Prevent it?
    • CallTower recommends that prior to filling out a new LOA form, ask your current carrier for a CSR. If they do not provide a CSR (some do not or cannot), ask instead for the relevant porting data. Porting data is verified against this CSR data, so if the carrier reports it to you correctly, you should not have any porting problems.
  • How Do We Fix It? 
    • CallTower will help you double-check the address for mistakes. Is it possible the address the LSP (Losing Service Provider) is using is not current; Could the bill be going to a service location different than where the phones reside; Is the Zip Code incorrect; Check all of these things. If they appear to match and no readily identifiable error exists, CallTower will have you request a CSR from the LSP.

Incorrect BTN/Porting Telephone Number Mismatch

This is the most common error, which means the billing telephone number entered on the LOA form does not match the one on your current carrier. The BTN is often the same as the account number and is often – but not always – the first or “main” number on the account. Unfortunately, while this all sounds rather simple, it often is not. For example, here’s one critical issue: especially with VoIP carriers, it is increasingly common that the customer's account may have more than one BTN, and in some cases, their phone numbers may all have their own individual BTN.

  • How Do You Prevent it? 
    • As before, ask the LSP for a current CSR and use that information to fill out your LOA. Optionally, inquire about the BTN information for all the numbers on your account.
  • How Do We Fix It? 
    • First, CallTower will let you know if all or only some of the numbers were rejected. Oftentimes CallTower submits the LNP orders for dozens of numbers, and just a few get rejected because they are actually under a different BTN. Once you know for sure what has been rejected, you will need to call the LSP and request either a full CSR or the BTN for those rejected numbers. Also, you should check internally; Sometimes, business managers are unaware that they may have more than one telephone carrier providing services, which confuses the porting request process.

Partial Port

CallTower sees this error most commonly when the BTN of the existing account has numbers that are being ported away, but there are still remaining numbers on the account at that carrier. For example, the customer has a block of 20 numbers, and the first is the BTN on the current account. They decide to port their numbers away but decide that CallTower only needs 15 of them, which includes the current BTN. This would leave 5 numbers at the current carrier. But because the customer has requested to port away the BTN, the remaining service would have no BTN. The losing carrier will reject that port request until a new BTN has been established by the customer for the remaining service numbers. 

  • How Do You Prevent it?
    • Be aware. Are you intentionally leaving some numbers at the current carrier? If so, you must contact the carrier first to ask if they need to change their account to support the LNP request. Optionally, you will tell CallTower you can request a termination of service for the remaining numbers at the time of port.
  • How Do We Fix It? 
    • CallTower can resubmit the LNP forms and request termination of remaining services upon port if that is what you need. If other arrangements need to be in place, you must contact the LSP and follow their guidelines.

Pending Order On Account

Typically, this is just an “oops.” It can mean that an LNP request is already being processed at your current carrier, preventing further orders. But it can also happen if an un-executed order exists, such as a disconnect order or a feature change request. 

  • How Do You Prevent it?
    • Often this sort of rejection comes when more than one person at the business is working on the same thing and have placed conflicting orders. Also, CallTower recommends that if you leave some service at the current carrier, wait until the port is fully completed and verified, and only then shut off the remaining service at the LSP. This will prevent unexpected obstructions.
  • How Do We Fix It?
    • Sometimes this rejection means that a recent order was canceled before completion and the new order overlaps. The only way to know is to contact your current carrier and ask what exists on their account that is preventing any new requests.

LSP Account Freeze

This happens more often than you would think. It means that the losing carrier has a hold on the account that prevents you from taking the service away until they are satisfied. There are many reasons they may and can do this, including but not limited to the threat of fraud or delinquency (you cannot port out numbers on an account that is not in good standing with the LSP). There are many less ethically challenged triggers as well.

  • How Do You Prevent it? 
    • CallTower again recommends that you check with the LSP before you order an LNP request for a new service.
  • How Do We Fix It? 
    • CallTower can’t help on this one. This is a conflict between you and the losing carrier that must be resolved between you two. You will need to contact that carrier to identify the barrier and have it removed.


  1. Ensure your current voice account is in good standing with your current carrier.
  2. Obtain a Customer Service Record (CSR) from your current provider, or if one is unavailable, request “porting data.”
  3. Pay attention to the numbers! Be aware of your current BTN and how that may affect the order.
  4. Review your account and ensure you have everything we need for a successful port. 


  • Was this article helpful?