Fed up with Absa

A few months ago my vehicle account was handed over to Mac Roberts attorney's by Absa vehicle finance even though I had made payment arrangements and I have never skipped a payment. I spoke to a consultant at Mac Roberts called Mashabela, he told me that it wasn't due to non payment but due to a discount that they wanted to offer me to pay for my shortfall. As my vehicle had already been sold in March 2013 at an AVAF auction after I had returned it to the bank itself. I was given the same payment details that AVAF had given me previously, accept for the reference number LV09048. Every month I have been making payments using the same details I was given, but I keep getting threatening sms's and calls saying they can't pick up my payments. I was told yesterday by Mashabela that his managers say I must go the bank so a branch consultant can trace my payments from last year even though I have sent them bank statements circling the monthly payments as they had advised me in December. I should have complained a long time ago about this but now I'm really fed up because this is not my mess up, I have followed their instructions from day one.