Incorrect Instalment on Credit Bureau

My account was handed over by Smart Advance to Nimble Group for collection. I made arrangements for and paid for over 6 months but when I checked my credit score it showed something that did not sit well with me. It showed that my balance is R18000 and my instalment showed also R18000. This error affects me badly on my credit report as other creditors sees that the monthly instalment is R18000 instead of the agreed R500 per month. If Nimble Group could change this with credit bureau I would appreciate and retract my review.