Amazon Prime Amazon Prime Membership has taken money from my bank account without my knowledge. Internet

Amazon Prime Membership took $100.25 from my bank account for a memebership fee I never agreed to. I have a amazon account that I've purchased from sellers online before, so I log on my account with Amazon and they ask me to try a 30 day trial membership with Prime??!!! UH....they took the money from my bank account without proper authorization, but they still asking me to sign up for a free trial. I have emailed them and waiting on reply, at this point I will never buy from Amazon or its sellers again. How did they get my bank info? since I log into Amazon my username apparently isn't matching up with my BANK account if Im still eligeble for a free 30 day trial. Hopefully this will get resolved, first thing in the morning Im notifying my bank!