harrasment from debt collectors

i have had the worst experience ever from a lady called janice naido, i had a homechoice account that was handed over , so i called NRB risk solutions to settle the account,The initial amount was R1100 and was handed over so i made a payment of R700 and when i called i was told that i owe 1900 and its because i get charged R500 each time i call and make an enquiry, Janice was very rude and that its not her problem, so what do i do in this situation as home choice cannot assist with the amount that i owe,