How can I cancel my 17 magazine subscription?

I Didn’t mean to order ten magazines from seventeen because I already have a two year subscription. I was entering the eyeliner sweepstakes and when it said would you like a years sub to 17 and I checked no, but when I clicked yes it said " thank you we will now bill you for ten magazines" Is there any way I can cancel that without canceling my previous subscription? I have not entered any info where they could possibly get a credit card or payment form either.

You should be safe if you did not give them your credit card number but call the 17 magazine number and tell them the mishap.