ER Consulting stop harassing me!

I have been harassed by ER Consulting and their debt collectors for over a year now because of the incompetency of their financial department. I paid my outstanding amount early last year but they keep sending me messages and calling me saying that I have not paid. I made countless calls and sent countless emails proving that I have paid but I get no help to clear my payment. I have even started to pay legal aid to assist me with this issue because I am being harassed daily for a payment that I have made and even when I try to resolve it nothing is being done.

Your financial department is very ***********, they can't even follow a simple instruction. I am sick and tired of being harassed by ER Consulting, I will not pay for a debt that I already paid for.