Radiuniverse.com — money taken off my card

I made an order from amazon and they were offing a trail membership to prime this was done on the 29th of june then on the 30th of june there was 48.00 dollars taken off my card. I did not authorize for that money to be taken off i would like to get my money back please. Then i believe i will cancell the prime if that is the way they handle business. That is just not right. Thank you for helping me get this resolved