one account, two attorneys

I have a FNB cheque account whereby I owe monies to.<br> In last year my cheque acc was handed over to Blake and Associates whereby an arrangement has been made to pay back the monies owed to FNB. My first problem is that these attorneys are situated in Durban, second, is that even after I have paid what I agreed upon I still get calls from different consultants harassing me. Unfortunately because they are situated in Durban, I cannot go personally to their offices to complain my issue with the consultants. During the month of November 2015 I started receiving messages from Hammond Pole Attorneys saying that this same cheque account has been handed over to them by FNB stating that I have defaulted on making payment to this account. At this point I suspect some foul play, as Hammond claims that I have not been paying on this account when I have proof that I have been paying the agreed upon amount with Blake and Associates. I need clarification before any further payments be made. Lastly no one can explain why my acc number is suddenly changed.