high settlement

I have an account with makro which I was planning to pay over 24 months. However when I asked for a settlement Makro charged me interest which I don't understand why as I am settling the account . They were suppose to write off interets and none of the 2 consultant explained why I am charged interests when setting the account. I am very unhappy as the point if settling is because I can't be able to pay the monthly installments and I am avoiding being listed