Managing the loan or lease: Vehicle loan or lease

I've been trying to pay off my loan faster with direct payments, but it's been 3 months and I can't. I've contacted the company several times and tried all the methods they suggested, but none worked. Trying an extra payment on the same day as the AutoPay transaction failed and was applied to the next installment. I contacted them again and they said they applied the interest first, even though I want to pay the full amount directly. They told me to pay on any day other than the AutoPay payment day, but that didn't work either and was applied to the next installment as a discount. I contacted them again and they said they resolved it, and told me to pay on the same day as the AutoPay payment again. I just checked and it's been applied to the next installment as a discount, contrary to what I wanted. I'd like to know how to pay directly through the app, or perhaps have them enable access so that any amount greater than the monthly installment paid within the month is automatically applied.