Harassment At its best

This Company does NOT follow correct procedure, they have been harassing my husband for weeks now, they phone from 7 in the morning continuously. They don't have the correct information, they put the phone down, they don't talk but worst of all is that my husband has required documentation from them over and over but it is not forthcoming. His payment arrangement was with a company he owed money to and NOT a debt collector, he has not made a payment arrangement with MBD as surely they are supposed to provide documentation proving they have taken the debt collection over? My husband has told them repeatedly he is not speaking to them until he has the documentation but they still keep phoning. Seeing all these bad reviews is very concerning as they don't seem to be very ethical.