Dstv charges fees for no reason

We upgraded out Dstv package from Compact to Premium in the 18 June. I was required to pay R177,67 extra which I paid immediately. I checked my balance due to pay today and I have an additional amount Of about 30 to pay that was carried over from who knows where.... If my calculations are correct, I should oy be paying my regular premium + insurance. I've pay an amount of R450 every month and never has an amount carried over, why now. I called your contact centre and the agent tried to explain it to me but it still does not add up. I'd like this resolved. Any extr amou ts I need to pay should have been noted upfront. If I was in a deficit when doing the upgrade, why allow the upgrade to go through or tell me I need to pay the excess amount in order for the upgrade to be successful. I have the screenshots of that WhatsApp chat