NTTA North Texas Tollway Authority Scam, Fraud what would you call it!!! Dallas Texas

So who do we complain to about the Fees and Late Charges from NTTA?? This appears to be an ongoing problem with them not billing until a late charge is applied. I sent my $ 3.36 for the use of their road and they sent it back. I cashed it and recieved another bill $13.36 with +$10 late charge. I called and explained that I had paid the initial fee and that it had been sent back. She stated that they did not recive it. after I told her I had a copy of the check sent and thiers sent back, she said I probably did'nt put my TAG # on the check. I asked her how they knew who to sent the check back too and she said by my name and address. Well I said could they not cross referance that to my bill and she said no!! So the problem is, this seems to be a problem so WHO DO WE COMPLAIN TO???