credit acceptance corporation still failing to reimburse wrongfully taken payment! southfield, Michigan

My husband and I purchased a car through Credit Acceptance Corporation, after having it a year the car was totaled and was paid off by insurance/gap coverage. A month after the accident they wrongfully took a payment from our bank account causing us to overdraft. I have called almost every day they are open since then trying to get this payment back.. there was a zero balance owed on the car when they took the payment. 

First I was told if I would fax a copy of my bank statement showing where they took a payment and it caused us overdraft they would expedite the process of getting it sent back to us. 5 weeks later we are still waiting. The company says the check was sent out 3 weeks ago and then a week ago and that I should give it up to 30 days to get here. I live in Alabama and this company is in Michigan, a hitch hiker could get it here in less than 30 days. Also we are not getting back the full payment amount... they keep telling me that there was interest that was taken out of the balance they are sending back. Interest for what??? The car has been completely paid off for 6 weeks. No one can tell me what the interest is for or when I will receive the check. I have been told 3 different times that it was sent out, only to call in a week when I don't receive it and find out it has not. I was informed by a very rude customer service rep that WHEN (not if) I don't receive it in 30 days call back and they will start the process of sending us another check.

This is the most horrible company I have ever had to deal with. Every customer service rep/supervisor has a different lie every time I talk to them. One supervisor (Valerie Finley ext# 0235) even called me "retarded" and accused me of lying. I am trying to figure out what my options are as far as filing a lawsuit against them, in the contract where we bought the car it clearly states that any over payment will be reimbursed within 30 days and 30 days was up about 20 days ago. They are liars and cheats and they should be shut down. All I can say is they better be glad I live in Alabama and not Michigan!!!