MTN Network has provided a link that people will join to connect with National ID card, agree they don't have to go to their office.
If you sign up they will send you OTP on the phone, which is some numbers you will add.
The things that are needed:
1. Full name, which is on National ID card.
2. Phone number.
4. NIN (National Identification Number).
For clarity on codes:
To retrieve your NIN: Dial *346*1#
To submit NIN to MTN
Dial *785*NIN Number#
If you don't have NIN, visit: https://www.nimc.gov.ng/