Unacceptable service

I upgraded my contract with Mtn for a tablet and took a new contract for my wife in August 24th 2015.I specified I wanted them capped at 0 so that I pay same amount monthly.169 and 149 which was supposed to b 320.In September I was debited 377,I did not complain, Last month I was debited 1365 and I went to enquire this at Greenstone and was told it was an error and it will b fixed, ref nr ***,this was not done and I reversed it,Dimittar assisted me as Mothusj was on leave,This month I got an sms that 1667 will b debited in my account and I forwarded it to him to make sure it doesn't happen , he said its o d Que to b sorted, This money went off my account again ,Such inconvenience and poor service I don't need I my life,I can't keep on reversing debit orders I my account due to mtn 's incompetence.They can take their tablets back if need b I want nothing to do with them now ,I will even change my prepaid number if I have to,who gets debited 1667 instead of 320.I will take this to the media if I have to as well as involve my lawyers.I need this nonsense sorted out Urgently. I deal wuth ppl and I know how to service people ,