HELP ME PLEASE!!!! I NEED ADVICE!!!!

I received a text in February about a $200 gas voucher and I naively became excited about it because I wanted to give the gas money to my mother as a gift. So I stupidly called the number. Long story short, it was from a "company" called "Central Rewards" and I stupidly gave them my information and they charged me a couple of times until I realized that this whole s**t was BU***HIT and changed my card number so they wouldn't be able to charge me any more. Since, I've still been receiving unwanted magazines in the mail.
NOW they are saying I owe a lot of money to them and that if I don't pay it, the amount will go into "collections." Should I believe that? What I'm worried about is if this will effect my credit...but I don't no if they're lying either. What should I do? What should I believe?