DEBT REVIEW UNJUST INTEREST CHARGED

Good Day I would like to inquire about my debt review, I was with Consumer Debt Help and Hyphen PDA was doing the payments deductions and in turn all relevant accounts were being paid. However i received a statement in march of 2019 i think and it reflected i had one last payment to go off for fnb in April. I then received another statement in April and it showed another pmt i think for R90 odd when i inquired about this i had been advised it was a mistake and the debit order would be stopped. After June i was then contacted to be told I owe fnb almost 6k when i started looking this and received a statement from fnb it all reflects as interest which adds up to the outstanding amount. My issue is all the interest amounts were charged on the 25th of every month. Now when i am querying this with fnb i am being told this is as per my agreement with the debt councilors. Firstly this is not my agreement and also my agreement was that the debit order was to go off on the 26th of every month yet they had only debited m on the 27th of the month and payments were only being allocated by latest the 9th of the following month. My question is why should i be liable for interest being charged before a debit order has even gone off. Also this is something the debt councilor was supposed to have made arrangements for so in actual fact this is their issue to resolve not mine. I have paid all of my debt and received paid up letters for all other account but just have a issue with this one. I actually refuse to pay this interest amount as well as it is unjust and unfair. this is why people never get out of debt review due to issues like this. I am needing the relative company to look into this and give me a very clear breakdown as this is ridiculous