Breach of agreement

I Mzwandile James, I requested absa vehicle finance to drop my instalments on 13 December 2018. We agreed on adding some cash (R20 000,00) and they promised to reduce it by R600,00 monthly. Only to find out in my December 2018 debit odder that they only reduced R300 instead of R600 we agreed on. Then I called vehicle finance and the lady by the Portia gave me an email address of ********** to send proof of payment which I did. I called vehicle finance again and Kenisha told me that Portia was the one who supposed to deal with this matter. I spoke to their team leader by the name Brendon. Brendon promised to call me after few hours, until to date there is no response from the their department. All I want is my money back (R20 000,00) so I can continue with my instalments normally. Howard centre, Pinelands, Cape Town branch gave me proper service and assistance regarding everything.