JP Morgan Chase Reversed charges for unauthorized transaction but later took them back alleging that transaction was authorized ( it was NOT) Internet

Back in December 2012 I noticed a charge for $900.00 for a repair shop in Georgia (I live in Miami). Since I did not authorize that charge, I called Chase, reported it and they reversed the charges and said they would investigate. So far so good, they would see that it indeed was an unauthorized transaction.

In February of this year, I check my account again and see that Chase took back the $900.00 from my account! I immediately called them and they argued with me that it was an authorized transaction because the person at the repair shop (the thief) had even given them my address and they have a signature. I endlessly told them that it was not me but they said they couldn't do anything and to try to solve the problem with the vendor. I asked them to send me a copy if the receipt because I wanted to see this 'signature'. When I finally got the copy, the signature on file was nothing like my signature!!!! The person had used my debit card number to pay for repairs on a BMW and used my address as a reference. So now I feel helpless because Chase simply took the money from my account without even asking. When I called the vendor, they said that they are sick of Chase because this is not the first time they take money from them too! The vendor had not received anything from Chase either!!! I am not sure about what I can do right now. It is unbelievable the stance that Chase has taken towards this. It was pretty much like, oh well, sorry Charlie. Has anybody been in a similar situation? How can I resolve anything?