wrong billing

Supervisor want to tell me the customer that I was out of airtime that's why they charged me for data use but when phoning 808 they say how much airtime you do have now and what he see on the system was also incorrect but he want to tell me the system is right and the 808 operators need more training that's why more people are moving away from them I can't wait till my contract end in november 2015 that I can change to pre paid and the customer must phone back 48hours later they cannot log something on the system that some one can phone me back. I was a customer of mtn for 14years and will not join there network again.