Porting your number to ONSIM is usually a seamless process, but because the UK telecoms network relies on exact data matching between providers, even a tiny typo can cause a rejection.
If your port request has been declined, don't worry—it’s usually a quick fix. Below are the most common reasons for a rejection and how to resolve them.
1. Postcode Mismatch (The #1 Reason)
The most common cause for a "Data Mismatch" rejection is the installation or billing address.
The Issue: The postcode you provided on your Letter of Authority (LOA) does not exactly match the records held by your current (losing) provider.
The Fix: Check your most recent bill from your current provider. Ensure the postcode matches exactly, including any spaces. If you have recently moved, the losing provider may still have your old address on file. We would recommend checking the address with your losing provider.
2. The Number is Inactive or Disconnected
To move a number, it must be active with your current provider.
The Issue: You cancelled your contract with your old provider before the port was completed. Once a line is cancelled, the number returns to the original range holder and "dies," making it nearly impossible to retrieve.
The Fix: Never cancel your existing service until your number has successfully landed at ONSIM. If it’s already disconnected, contact your old provider immediately to see if they can "re-bridge" or reactivate the line temporarily.
3. Pending Orders on the Account
Providers cannot process a port if there is another "open order" on the line.
The Issue: You might have a pending broadband upgrade, a change of address request, or a recent plan change that hasn't fully cleared their system yet.
The Fix: Wait for any existing changes to complete (usually 24–48 hours) and then resubmit the port request.
4. Incorrect Service Type (Single vs. Multi-line)
This is specific to landline/VoIP ports and is a frequent "gotcha."
The Issue: You submitted a request for a Single Line, but the number is actually part of a Multi-line setup or a DDI Range (e.g., an ISDN block where you have a main billing number and several extension numbers).
The Fix: Confirm with your current provider if the number is "Single" or "Multi-line." If it's a range, you must provide the Main Billing Number (MBN) even if you are only porting one specific extension.
5. Invalid PAC or STAC (Mobile Only)
For mobile ports, the "key" to the door is your PAC code.
The Issue: The PAC code provided has expired (they are only valid for 30 days) or was entered with a typo.
The Fix: Double-check the code. It should be 3 letters and 6 numbers (e.g., ABC123456). If it’s over 30 days old, you'll need to request a new one from your old network.
💳 Porting Fees & Costs
Please ensure all details are 100% accurate before submitting your request.
Port Resubmission Fee: There is a £20 + VAT fee for each port resubmission required due to incorrect data.
Provider Rejection Fees: ⚠️ Note that some losing providers also charge a "Rejected Port Fee" for failed attempts.
To avoid these unnecessary costs, always verify your exact billing address and service type with your current provider before submitting your LOA.
🛠️ How to resubmit your port
Contact your current provider: 📞 Ask them specifically for your "Porting Validation Data" (Address, Postcode, and Service Type).
Update your LOA: ✅ Ensure all details match their records exactly.
Contact ONSIM Support: 📧 Send the corrected details to us, and we will restart the process for you.