This is a trending topic at the moment in the whole city of Nigeria as MTN Nigeria is blocking those sim cards that are yet to be fully registered.

Here ia a tip on How To Use BVN To Register Your MTN Sim Manually

The use of BVN has been introduce to avoid too many crowd in their respective offices.MTN can not just go ahead to Use BVN To Register Your MTN Sim Manually without your knowledge and approval hence, they would want you to send a command text message, Send “Yes” to 799, This will fully give them the access they need to use your BVN to complete use BVN to register your MTN sim manually

MTN also assures that this process will only work when you use the sim you used in registering your BVN in the bank for this exercise, so if you want to register a fresh sim, or doesn't have a BVN you would want to visit their offices to get your sim registered, so that your sim will be fully activated.
READ MORE....http://ucgist.com.ng/how-to-use-bvn-to-register-your-mtn-sim-manually/