Mtn are ******!!!

I am so depressed right now. Mtn people had been overcharging since October last year and as soon as I picked that up I informed them. They admitted to the mistake from their part and promised to refund me. True to their word I got my refund in May of about R1600 and they said the other amount was credited to my mtn account. I didn't have a problem with that since it meant not paying for June. To my surprise on my payday last month R3900 was deducted from my account! When I enquired about it I was told they had paid me that amount on the 30th of May!!! After a lot of arguing they asked me to send them my bank statement of which I did. After realizing that amount wasn't paid to my account, another apology was tendered and I was given an assurance that it was going to be fixed. Mind you the time the debit order bounced I also incurred bank charges and a negative credit record ????. On Monday, my line was suspended because allegedly I am owing R3900!!!!! I tried calling but was taken from pillar to post. When I finally got unblocked I received a message saying that I have made a promise to pay that money after 1 week, I mean what the hell!!!!!! Please sort this out as it is affecting me very badly