Following the order by Federal Government that all telecom operators should block all sims not synced with the National Identification Number (NIN) within two weeks (from December 16, 2020 and end by 30th of December 2020).
Here is how you can link your GLO SIM CARD with NIN ahead of the deadline:
Text UpdateNIN [NIN] [FirstName, LastName] to 109.
E.g UPDATENIN 12345678903 Abdu Mohammed
To confirm if your NIN Number is linked with your SIM, see here.