To Check Your Bank BVN using code
Dial *565*0# from the mobile phone number (sim) you registered with your bank account. This code works for all banks BVN on MTN, Glo, Airtel and 9mobile lines.
GTBank Code for checking BVN
You can also use GTBank code for BVN checking by dialing *737*6*1#.
NOTE: You need N10 airtime balance for it to work, because the checking is not free.