ABSA Credit Card ***** - bad credit on my name

Someone used my card for online purchase with Gumtree. I reported it to ABSA ***** division shortly after I received the sms. The purchase was complete and caused my account to go into a serious negative. They are now going to report me to the credit bureau because I can't pay the money back or the bank charges and keep sending me sms'es to tell them i owe them money..

ABSA should have declined it for insufficient funds in the account like it happens in supermarkets. I have to wait 30 days for the investigation, but I want my name cleared as it was their fault and why 30days???