Fifth Third Bank Has been debiting my checking and they were never authorized to do so. internet

I have just discovered that Fifth Third Bank has been debiting my checking account that I have at a different bank. They were never authorized to do so. I have tried for weeks to speak to someone that can help me but have been told I have no account with them. They have no information in their system for me, so they say. I want to know why they have been taking my money and I do have 2 years of bank records from my bank to prove they have been taking a monthly fee from my account. After  weeks of calling them, someone finally found records on me and they say I signed a contract for a credit card machine for my small home based business. I asked them to fax me the contract I supposedly signed and it is NOT my signature! They admit I have never used their services. They are refusing to refund the $800+ dollars they have fraudulently taken from me. I believe they are bullies and rip-offs and I am going to have to pursue getting my money back through the courts. I work very hard for my money and am now going to have to work even harder to try and get back what is mine.