Im being overcharged on loan

Beginning of the year I took out two loans from capitec totalling R23500. The agreement said that interest and service fee was included. The other day I went to get my statement and it showed that they were charging me seek separately for the interest and service fee. I was surprised because I knew these amounts to be included in my instalment, that's what the agreement said. This has the effect of increasing my loan balance but I never missed a payment. I want to know why we agreed that the instalments will include interest and service fee but they charging me separately even after I make payments monthly on time.