Harassment

I had a Truworths account with MBD I was making monthly payments of R150, I received a call from a consultant in July 15 offering me a discount if I made an payment of R2427. the account would be fully paid. This payment was made 27 Aug 2015. I did not hear from them again. At about Nov 2017 I started getting harassed with and SMS calls that I have an outstanding amount of += R4000 . I told them that I received a discount, but they do not have proof I must give them proof, I requested a full detailed account of all transactions on my account, they keep on sending me a summary. I want to see all payments made on that account and all the legal fees allocated. Surely the should have proof of the call made to me as they record every call.