Product: Vehicle loan or lease

On XX/XX/XXXX we began making aggressive payments on our auto loan, the first amount being {$1100.00}. From then on, we made 8 payments, each daily totaling {$3000.00} until finishing paying off the total amount of the car on XX/XX/XXXX with the last payment being {$2100.00}. All of this totaling {$27000.00}. Then we received the letter from ally stating that our vehicle was fully paid off as of XX/XX/XXXX. Then on XX/XX/XXXX, my bank notified me that Ally had additionally withdrawn 2 payments of {$3000.00} totaling {$6000.00} after my vehicle had been fully paid off. Upon investigation my account on Ally doesnt display these additional transactions ; my bank statements however, do. 
On XX/XX/XXXX I called Ally customer service to inquire about these additional transactions that I did not authorize. They claimed that they had no record of the additional charges of {$6000.00}. After a bit of back and forth, the customer service representative informed me that they spoke to another department in Ally and they had record of an additional {$3000.00} charged after the vehicle was paid off, but not the full amount of {$6000.00} that they charged me. They instructed me to fax ally a copy of my bank statements for the period of time that these charges occurred, along with my ally account number, and to request reimbursement. On XX/XX/XXXX, I faxed to Ally Auto a copy of my reimbursement request, bank statements, the letter stating that Ive paid off my vehicle in full as of XX/XX/XXXX. 
On XX/XX/XXXX I contacted Ally Auto customer service again to verify that they received my faxed documents and when to expect my reimbursement. The customer service agent claimed that there were no charges that occurred on XX/XX/XXXX, that they had no record of these charges being made, that they never received {$6000.00} on XX/XX/XXXX, despite what my bank statements say. They could not transfer me to a more helpful department. They requested that I wait 20 days for these charges to show in my account, they also offered no callback numbers or any recourse to take should these charges not be automatically refunded after the 20 days have passed. It was on this day, XX/XX/XXXX, that I sold the vehicle, a XXXX XXXX XXXX, to XXXX as Ally was no longer the legal owner or lien holder of the vehicle. 31 business days after the charges were posted, on XX/XX/XXXX, I contacted XXXX XXXX XXXXXXXX to file a claim as Ally had withdrawn the {$6000.00} without my permission and without cause. 
I received 2 temporary credits, each for {$3000.00} for each fraudulent charge made on XX/XX/XXXX. After which, on XX/XX/XXXX, Ally sent me 2 emails informing me that they had returned 2 payments I had scheduled and completed towards my vehicle on XX/XX/XXXX, each for {$3000.00}, not the 2 fraudulent charges made on XX/XX/XXXX, and is now claiming I have a remaining balance of {$8600.00} ( {$6000.00} of returned charges with {$2600.00} of retroactive interest ) on a vehicle I had fully paid off as of XX/XX/XXXX. As of XX/XX/XXXX I have received notice that the loan balance is being written as charged off and have reason to believe that Ally is attempting to sell this erroneous debt to a collections agency after denying us recourse and refusing to resolve the matter.