This wasn't anything to do with WGT.....unless anyone actually believes WGT would single out 1 person from the many 1000's of folks who use their cc to buy stuff from WGT.
It has 3rd party scam written all over it.
OP should do as Icon says and call his cc to cancel the old card and re-issue a new one.
And while he's at it, do a strict security check on his system to remove any naughty stuff hiding on his hard drive, because that's where the security breach originated. If there's one, the chances are there may be others too.
I generally recommend a complete hd reformat when this happens to be sure it's gone and that any of its friends aren't just hiding in wait for an opportune moment either.
By the sounds of it...it was browser cookie related adware and by all means a relatively minor intrusion. More serious ones just ding the cc and the 1st time you'll notice it...is when your monthly cc bill arrives & Blammo!!! someone somewhere in the world is living like a king....free gratis at the courtesy of your fantastic plastic.