listed as a default on ITC with incorrect amount

In december 2016 i hired a vehicle at OR Tambo internation and returned on the agreed date. two days after the drop off i received a call to say that there is a damage on the vehicle, explained to the guy that the damage was already there and sup**** proof to that extend. however months after that i received an sms to tell me that i owe them R3577 and i ignored it since the matter was settled. in september i received the same sms and i tried to contact the person who appeared at the foot of the sms.

October i realised that i have been listed on ITC as 'default' and my account has been handed to MBD inc for collection. I then it took serious and contacted the person who is responsible for such and he greatfully managed to resolve the amount on the invoice and a revised invoice indicated that i owe AVIS R1377 for extra milage travelled. I did not contest it and went to pay the amount in full

Why must i pay MBD's collection fees for work they did not do? Where is the recourse for being listed? What are the requirements for a company to list an individual?