Continuous Incorrect Billing By MTN

I've been an MTN contract customer for years and the problem started when they billed me incorrectly last year.<br> I requested for the usage to be validated and the proof to be sent to me. They credited my account but not the entire amount and they never sent me proof of my usage ***. After months of waiting for proof from the call Centre agent Lerato Malema I decided to pay and move on because they'd already suspended my line. The issue reared its ugly head again in September where they billed me R1200 more than they should have, Andrew Crouch in call centre *** never escalated despite validation confirm that indeed a credit note was due. In the middle of that (13/09/15 ***) I went to their store in Fourways mall to put a request to migrate me from contract to pre-paid. On the 6th of Oct I followed up both queries Agent Qoli Nzimande re#*** & #*** respectively. I settled the September bill and then for October the retention Agent wanted to persuade me to reconsider to which I declined but he went ahead and migrated me. I didn't receive Oct invoice but SMS saying I owed R830 which I paid R850. Today I received another SMS for R2 391.27