Biotab Nutraceuticals / Extenze BIOTAB NUTRICEUTICALS INC BEWARE "EXTENZE" RIP-OFF, Internet

I made the  mistake of ordering EXTENZE! I sent back there full unopened order and requested them to stop billing me. Extenze just keeps on billing me .they have these ladyies call and say they have a much stronger pill-'Its all B-S'- I say I cancelled and I could hear them laugh as they say' you get  conformation of this' -They just hangup (without even saying goodbye) and move on to the next sucker as fast as they can... 

I still haven't recieved any conformation from them and expect to be billed again and maybe again-How can I stop them? I sent there product back (paid for ups) emailed, phoned , thier laughing in my face for they have my credit card info and $49.95 every 30 days...Help for I don't know what to do short of cancelling my card...