I am not paying for MTN mistake

My account was upgraded via telephone from MTN headoffice. But the upgrade done was incorrect. I previously had a package that had a limit on. when the upgrade was done, the consultant never informed me that the new package does not have a limit. And he never put a limit on the account. So for 2 -3 weeks my account was open. It was only when I went into the store at Mall At Reds, that the consultant there informed me about the wrong upgrade. He then cancelled the upgrade but battled to put a block back on due to the MTN Server. You can contact Jay at Mall at reds to verify. I have spoken to so many people at MTN, i have so man reference numbers. The one lady that did try to help me, just decided that the data was used, and tough stuff. She closed my query on reference no ***. I have tried to speak to someone in Finance, becaues I refuse to pay for the excessive amount. But nobody gets back to me. I just get a sms saying that they are going to suspend my account, and hand me over. Wow, I have been a customer for more than 15 years. I am really disappointed at the red tape involved in trying to sort out something so simple.