Incorrect billing and NO FEEDBACK!!

I've added a new phone/device to my MTN contract at the Woodlands store in Pretoria East, more than 4 people worked on it in order to add it because nobody knew what they were doing. Once it's been sorted we paid for the initial fee, and started using the phone/device, when it came time to send a statement it showed that the total amount was R1200 and not R250.00 as ADVERTISED on their PROMOTION!! I printed the statement, went to the store and they informed me that it's only the amount that it would have been if it wasn't on PROMOTION! I asked them if they can guarantee me that the amount will not go off and that only the R250 will go off from my account. Their answer to me were, the amount will not go off and the head office will change it so that only the R250 goes off and I can go back to them if the full amount went off. So I ended going back because they took off the FULL amount and not just the R250. I asked them to fix it because I DID NOT authorize the R1200 to be deducted from my account. All they could say is that they will look in to it. 3 weeks passed already and I've been to the store more than 5times to get feedback because evertime they tell me they will call me before the end of the day. THEY NEVER PHONED. The only answer they have is that it's been escalated! How many times does it need to be escalated before something is sorted. I'm sick and tired of this pathetic service that can't give you feedback regarding an incorrect billing because THEY decided to add more data to the contract without any approval??? It is just as good as *****!!!! I will go to every measure to make sure that the people who worked on the account will be held responsible!