NEDBANK Bad service credit card limit & card specialist

Been 2 months since Nedbank made a *****up with my creditcard, several emails sent and complaints lodged. everytime it is escalated but when I enquire then nobody reply's or wants to give me feedback....

My credit limit was increased, after I used the money they call me and tell me they made a mistake it should be less and I must pay the money back. I refused as they made the mistake and they said fine, pls send us your bank statements and a card specialist will rectify the issue and ajust my credit so that I don't have to pay the amount back. that still hasn't been done and now im getting calls telling me that im overdrawn and in arreaers. why must I be pay for a mistake they made ( and promised to rectify )