Paying loan that increase it balance but not decreasing

I made an early payment on my loan since I got paid earlier than the usual payment day. Then on the payment day, they debited the payment again. I followed through and requested a reversal on one of the payment since I paid double. Then 3 months later I noticed that my loan balance is increasing instead of decreasing. So I checked my statement, only to notice that they added extra money as areas that is equivalent to my monthly premiums. That means they regarded that one reversal as if I never paid at all. But when I call and enquire about it. They simply say it's the areas that I've accumulated. So I asked how since I didn't miss any payments. So the people I spoke to they just said I need to increase my payments. But how I accumulated the areas I don't know. I requested a review on that months I paid double for and reversed that other amount. The person just said i can't be failing to pay my loan and tell him what I want him to say. And my loan has remained stable on one point coz I'm paying the amount equivalent to the December areas they added. Now I've lost R10 000 without any movement. And the balance is increasing