american credit acceptance fees to pay online???? fees over the phone??? st louis, Missouri

Ok.. so they called me at work 3 times a day for two days, then come to find out that they apparently
hadn't recieved a payment that I had made by check. I was told to pay over the phone, or even
better, over their web site so that late fees could be avoided. Well, next payment I made was by phone. I was charged a $10.00 "convienience fee" that was strange, but I thought I'd just use the web site for future payments. At the end of the process I was informed that I was being charged a (u guessed it) $10.00 fee! So, my question is, how do you pay your car payment withOUT being feed again?? Is it possible? THEY referred ME to the website to save money......anyone understand this?