The charge should have a company name beside it on your credit card bill. If there is no phone number listed, do an internet search on that name for a phone number to call. You should also be able to get the info from you credit card company. I had this happen and I found the business' number, called it and had the charge dropped.
If they are uncooperative when you call, ask to talk to a supervisor. Be sure to write everyone's names and titles down that you speak with. If that supervisor does not bend, get his/her supervisor. Keep going up the chain untill you get results.
If this doesn't work at first, call the better business bureau and file a complaint (www.bbb.org). Keep calling and harassing them, let them know you have filed a complaint, and keep after them until they refund your money. They should break eventually.