Why hasn't a successful recharge been credited to my account ?

I made a recharge of 500 naira today and I'm still yet to see It credited into my account although customer care says that a sum of 377 has been deducted for outstanding extra time but that is a lie because this is my second recharge and my first recharge or 500 naira paid off that debt so how can I be deducted twice for an outstanding debt and the fact that I can't even say the second recharge reflected in my account at all is a problem and customer care is not giving me a reasonable reply what is the problem? what do I do?