Service sucks

I have been a customer for over 10 years however, the last 2 months has been the worst first I couldn't use my data and then they purposely take long to investigate and close the ticket on the day your new minutes and stuff comes in without explanation. This month my line has been suspended for non payment more times than one can even count even after sending proof of payment and the credit management department saying all is clear. I have tried cancelling this contract for the past month as I cant deal with mtn any longer, retentions doesnt answer and when they do you get told their systems are offline.