FNB and Debt Collectors

I have little or no experience in the Debt Recovery business but am frustrated and upset that after forwarding FNB my retrenchment documents along with doctors reports, I continue to be harassed by Debt Collectors acting on behalf of the bank. I am now 65 and even if my asthma was not chronic, how on earth would I be able to get a job. So I have to continuously point out to them that I have little or no income and so cannot make payment arrangements if I cannot make payment. They continuously hand this debt from attorney to attorney. Can someone advise me what to do or maybe I must just ignore them.