I would think your best shot would be to call up Blizzard on the phone and tell explain the sitution in person first and if you have the orginal reciepts that could go along way into helping you out. Other than that you'll probably have to end up buying up a couple more copies and releveling a few toons.

I ended up having to do the same thing. My roommate ended up installing my first copy of wow back in the day since i had to run off to work and the install took so long. W/o thinking about it he put his own name into the account creation info. Anyways long story short when I started multiboxing some of the accounts where in my name, some in his even though I legitly bought all the copies it wouldn't have matter. If I had gotten caught, which i never did, I would of lost at least 3 of my accounts and all the work that went along with it.