Unfair credit practice

I had borrowed money in 2021 so I requested that I pay the monthly of R69 upfront on the contract which they agreed on.i paid a lump sum of over R2000 with the mind that the instalment will be reduced and interest. Direct axis has decided to park that amount as an advance and still charging me the R69 monthly since inception of the contract. I need that money capped and reduction of instalment.