To check your airtime balance
MTN Awuf>> *559*14#
MTN >> *556#
GLO >> #124*1#
GLO 5x >> #555*5#
AirTel >> *123#
Etisalat >> *232#

To check your data balance
MTN (SME) >> *461*4#
MTN (Corporate) >> *312*4*7*4#
MTN >> *131*4#
GLO >> *127*0#
AirTel >> *140#
Etisalat >> *228#