MTN *****ing customer Airtime and poor network coverage

I have a serous problem with MTN i bought MTN airtime R60 yesterday in the afternoon and i convected R20 to 45 voice data and i made one call that took 2 minutes but when i check the balance there was no airtime and it is not for the first time complaining about this issue on MTN and it has been happening for quite some time now and when i complain to them they defend themselves saying i made calls that i did do because my phone has a password and they always giving me my second number claiming that i hqve call it and which is what i am disputing. And the poor network coverage makes me Sick!