ripped off

found they had been taking out 19.99 a month that i did not sign up for,they claim i signed up over the phone,i know its not true i dont sign up for anything over the phone,they also said i received a gift card for,one person said 30.00 and another claimed it was 40.00. this company is nothing but a rip off,i dont know how they even got my credit card no.does anyone know how they get it?