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 9mobile SIM CARD with NIN ahead of the deadline:
Dial *200*8# or visit https://nin.9mobile.com.ng/ and proceed to input your NIN.
To confirm if your NIN is linked with your SIM, see here.