Bad Customer service

I phoned the call centre and spoke to Thembiso Nyambo on 29th and was given a higher amount for my contract when I queried she insisted that my cell phone contract went up and that I was advised of it.I requested proof of that and also requested a statemnt which I never received.even thought I told her that my contract was already increased once this year she said that they received a memo advising them that all contracts were going up, instead of just checking the statement and seeing that it was an error on mtns billing part. Luckily I called again yesterday and spoke to Beverly and was advised that it was an error on mtn billing dept part and they will rectify it. I appreciate her help as it was better than thembiso giving me incorrect info. But I need a response quicker than the 21 days that I was asked to wait, as I have other debit orders and now I am goin to have to 1stly pay for unpaid debit orders,also what of it is not rectified before the next billing date then am I going to be charged extra again. I understand everyone makes mistakes but this is not right. I have 3 contracts with mtn but I am seriously considering changing providers as the customer service is pathetic