I had the same problem last time, some one was using my credit to make phone calls while I still have the card with me...The credit card company called me and asked me whether I made those transactions. After I told them I did not. They terminted that card and issue me a new one. However, the charge still showed up on my statement. They mailed a form for me to conplete to indicate which charge is not mine and they credit me for that amount after they received it.

btw, I paid for the entire amount for the billing and credit card company credit the amount the next billing cycle.

I think you should call them again and get advise from them and remember to wirte down the person's name you talked to and time you called.