Harassment

I am constantly receiving 2-3 phone calls per day from consultant harassing me. My account is paid up as per telephonic conversation we had in the beginning of July this year .I was told the amount due is just over 800 so I had the option to either settle the entire amount end of July or continue to pay the outstanding amount in 2 months. I pad in 2 months and the last installment was deducted from my account end of August this year .I have requested paid up letter and I am getting is harassment from consultants demanding different amounts one is demanding R 269.00 others are requesting R 400 and one is demanding over R 1000. All I am asking is for a manager or supervisor to revert back to me in writing as every time I received a phone call all I am getting is harassment .