Credit Acceptance Corperation Not posting payments and harassing calls saying Im a month behind and tring to repo before my due date. detroit, Michigan

The Company say I'm behind one day then current two days later. My bill isn't due till the 23rd of every month, I pay every week and I'm still behind. I made a 500.00 payment and my bill is only 460.00, they call me everyday to tell me I'm still behind.If I don't make my payment by the end of the day then in schedule for repo. I arrange to make a payment, I keep up my promise and still get harassed everyday. Day one since I brought the car I've made payments every week but I'm a month behind? Incredible! Pin this! I made a payment for one week and they still called me the same day I made the payment to tell me I still need to make a payment. How genus is that. They really need to get it together!!!