No-one can explain or reverse mystery charge on credit card

A mystery FEE, INET/MOB FEE/FOOI came off my credit card at the beginning of September. Since then I have been passed all around ABSA, but no one can tell me what this fee is, or why it did not come off the nominated fee account (the cheque account), not will they reverse it. They just hope I'll go away. At this rate, I will go away - I will be closing what accounts remain with ABSA.