Unfair customer treatment

I am very disappointed in the poor service rendered by this institute I made an incorrect payment to 1 of my decoders in September and requested for this to be resolved on the 23/09 their consultant advised me that I had to use that decoder as they could not allocate payment to my preferred decoder and I agreed. Today I was disconnected and when I called I was told I am owing them because payment was moved and I was viewing in credit and I have never known DSTv to do this. When I asked to log a dispute so that they could investigate by listening to the calls the consultant Karabo wouldn't listen. So they were telling me the R400 payment I made for October was used up as September payment and the team leader then said I should pay R125 . How is it my fault? Is Multichoice that unprofessional that they are not willing to investigate matter to decide the next course of action but would rather penalize customers.