What is most likely is that either (1) Someone you know created the account (Relative, sibling, spouse etc.) or (2) Someone gave the wrong credit card number when setting up their account and accidentally transposed a few numbers resulting in *your* credit card being charged, instead of theirs. Like 123xxx123 which is your credit card instead of 123xxx132 which is theirs. I saw this with some regularity when I was an ISP rep. What was even neater was when someone else's phone bill would be charged for someone else's internet service because the original account holder have changed their number, didn't update their billing information, and someone else inherited their number (this was Ameritech.net) and got billed for internet service. Lovely thing was that we had to send them a check which would take a few billing cycles PLUS they might get billed again, because of how the billing system worked... 
And oh, by the way, they probably won't allow you to close the account if it isn't yours. 
