Poor of service

My account was made paid up in May 2015 but there is still a interest showing on the Fochini account even after receiving a paid letter. This interest has not been cleared from my name since 2015. I called the call centre and was advised that it will take 3 working to clear this interest, The call centre agents will never show any interest in the call. For something that was supposed to be cleared in 2015 is still not resolved.