I paid these guys R900 when I was told to pay just over R800 but the account keeps accumulating from zero which does not make sense to me and they keep harrasing me saying I owe them R145???? I dont owe these guys any money

I paid these guys R900 when I was told to pay just over R800 but the account keeps accumulating from zero which does not make sense to me and they keep harrasing me saying I owe them R145???? I dont owe these guys any money. Is these how these guys make money from people. How is this possible??? I owe you R800 and I pay u R900 and I still owe u. Someone pls make sense to me😭😭😭