Account handover by Europcar

Europcar hand over my Account to hybid collection on the 20/04/2018 after I paid R1000 on the 17/03/2018

Herecis the story..I hired a car from them through my insurance and wgen I bring it back they complaint about the dent abd I tried to tell them that I didnt dent the car but they insisted me to pay a R3000 of excess and I did that in March then in April I received a call frm hybrid collectors demanding me to pay R3310 and I explained to them and I even sent them the proof of payment asking them how could I pay R3310 offwhich I already I already paid R1000 and I continued paying R500 until I paid up my account...The problem niw us HYBRID COLLECTORS are continuing askibg money from me and I asked what for because I never refuse to pay money and money is paid up abd tgey said I owe them and today they said +_R500 and they sent me a statement reflecting R1000 that was paid in July 23 abd I asked them how because proof of payment shows 27 march and the calcukation where done by R3000 ..now I need assistant because to me I just see them as yhey are taking advantage and tgeir are fircing me to pay the remaining amount offwhich I dont understand EUROPCAR, how did they handover my account while I paid yhem and I did negotiations to pay them by instalment and I refused to pay but Im worried about my reputation