GE Capital Auto Financial Services Payment Nightmare

I have been fighting with GE Capital over a mis-applied payment since December. I have sent them three copies of my check prooving my payment and they still insist they can't see where the payment was applied. I feel I have gone beyond prooving my payment was made... now it is up to them to find out where they applied it.

My bank can't send me the original check because they discard them after they make a copy. What am I suppose to do? I get phone calls from them everyday about me not making the payment. Everytime I make a payment, it is applied to the so called past due amount but I'm actually caught up. I'm so frustrated... I want out of this car loan just to get rid of them.

Everytime someone calls me, I have to start over explaining what has happened. Does anyone know where I can go above these customer service reps heads? I really need to get in touch with the accounting department or something.