Poor service and billing

I went to MTN morningside to get a new phone in February 2014. I received the phone and used it but when i received my bil at the end of the month, it showed that i owe a large amount of money which was not the option i choose. I then went back to Morningside to inquire about the bill and they realized that the previous agent never capped the phone. I then queried the matter and a case was created and the agent said that they will call me within ten days, which they never. I later went to Morningside again and i was assisted by the manager Dushen who said he will investigate the matter and get ack to me, which he did not. I then got fed up and went to MTN 14th avenue which they said they could not help as the matter is related to a store and i need to deal with them directly. I then sent Dushen numerous emails asking for feedback but never received any. I have recently went back to Morningside and didn