The co. reps. try to convince you that you are wrong. I've had to call over 6 times regarding having add'l funds applied to principal. Their software doesn't have the capability to do it for future payments. They have tried to apply extra payments to later payments rather than the ones months earlier. Their response is that it doesn't matter. So, according to them, paying more toward principal doesn't affect your interest payments even though interest is calculated daily. I was told that HMF is separate than the car co.. I have so say that I'd be much less likely to buy another Hyundai after this experience. I had had Fords and VWs prior to my switch to Hyundai after the diesel settlement. It's a shame that poor customer service will lose a potentially loyal customer.