Extra interest charged

I had 2 accounts with African bank a credit card and a loan,which were handed over to creditworx,when I started working again I made arrangements to pay the accounts,which I have been paying for since 2016 to date every 3 months the the is a roll-up fee of added on the account,when you call to find out it's a blame game and the guys from creditworx say they receive the statement from the client like that,my argument is they are charging me interest on the account and collection fees but the is still a lump sum added,2017 April my balance was 8000 and they added 3400 and no one can account for that.they said they were escalating my account and will give me feedback that was a month ago,everytime I call I get an attitude from the creditworx consultants,I asked them to give me a collections department of African bank and they told me I must google.can someone help before I take this further,I need help asap