NTTA / overcharging administrative fees after payment made

On 3-15-17 I made full payment of amount due, come new invoice (3-7 to 4-7) additional amounts of 47.26 (.50 toll, 10.00 fee, 1.76 toll and 35 fee)owing. Then another invoice came for next months service and amount is up to 72.26. Tried to call after first notice and they had no information they could give me. Today, I spent over 45 minutes between ntta, payment solutions, alliance one, then back to ntta. NTTA credited the original 35 and I paid the .50 toll. They say they cannot do anything about the remaining 36.76 because it's already gone to collections. I called them to pay the bill, I am not avoiding my charges, I just can't get clear information. If there were invoices in between, I did not receive them. I am tired of hearing that no one can waive the amount in collections when I am a good customer and there are hundreds of people that don't pay their crap. At this point it's the principal of it. They have us all by the b-lls and it's not cool.