FNB Home Loans

I have a home loan with FNB Home Loans. I requested a debit order change, to change from one FNB account to another FNB account. My problem is that FNB Home Loan debits from both the accounts. Several times I phoned they only say there is nothing they can do but escalate to their supervisors, then they promise to get back to me and they never ever get back to me. I just wonder how will the employees of FNB Home Loans feel or what they will do if they get debited twice on whatever bills they pay.