How can I get back my lost sim not registered by me?

I am sorry about your missing line.

You will not be able to do a sim swap on a line that was not registered by you. However, ask MyCustomer who registered the line to visit our office nearest to him/her for assistance on the sim swap of the missing line.

Kindly visit any MTN office closest to you with a valid means of identification for assistance.
These are valid means of identification: Voter’s Card, Driver’s License, International Passport, National Identity Card, National identity Card (NIN) slip or letter of authentication by a traditional ruler or community leader affixed with a passport photograph in rural areas).

Dial *123*7*1#, follow the prompt so that you will be able to get the address of our office closest to you. You can also use this link https://www.mtnonline.com/stores to check other office locations.
To request for a welcome back or SIM swap at our office.

Kindly visit https://www.mtnonline.com/welcomeback-form or https://www.mtnonline.com/simswap , download the welcome back form and print it out in hard copy;
• Fill the welcome back form; and
• Finally, visit the nearest MTN office with the filled form and submit for your welcome back request to be processed for you. The welcome back fee is N400 (any additional fee requested must be credited to your line as airtime).

In addition to the phone number being registered by you, you are required to come with a valid identity card (Voter’s Card, Driver’s License, International Passport, National Identity Card, National identity Card (NIN) slip or letter of authentication by a traditional ruler or community leader affixed with a passport photograph in rural areas). NIN slip very important.

Most importantly, you are required to provide the SIM pack or other evidence of direct purchase/ ownership. Where the SIM pack is unavailable, a sworn High Court affidavit as proof of loss and ownership is required.
OR
To retrieve your MTN line,
Our service centers or connect stores nearest to you with the following:
Your Phone Number;

The SIM pack or other evidence of direct purchase/ ownership. Where the SIM pack is unavailable, a sworn High Court affidavit as proof of loss and ownership is required;
Year of activation;
Tariff plan (MTN Xtra special, MTN Pulse, MTN Beta talk, MTN Biz plus, MTN Xtra Value, MTN Biz plus or MTN Biz class);
5 Regularly dialed numbers;
A valid identity card (Voter’s Card, Driver’s License, International Passport, National Identity Card, National identity Card (NIN) slip or letter of authentication by a traditional ruler or community leader affixed with a passport photograph in rural areas); NIN slip very important
.
A welcome back pack fee of N400;

PUK number and Correct details of your SIM registration (Your full name, address and date of birth).
Below are Sim swap bundle prices and Bands:
In view of the NEW Cost of MTN SIM Card, which is N400, kindly view this update on payment for SIM swap:
SIM SWAP Bundled with N0 with no airtime (N400)–Band 1
SIM SWAP Bundled with N200 airtime or data (N600)–Band 2
SIM SWAP Bundled with N400 airtime or data (N800)–Band 3
SIM SWAP Bundled with N650 airtime or data (N1,050)-Band 4
SIM SWAP Bundled with N900 airtime or data (N1,300)-Band 5

The above Sim swap /Upgrade bundles are based on your purchasing capability and will not be forced on you. It depends on your willingness to buy.