Like P-K I do not understand what back charges or service charge accounts are and it would greatly help if more information were given.
One general point over catalogue debts in general, which does not seem to be widely known, is that in many cases no contract, and therefore no legal responsibility exists. Catalogue companies are in such a hurry to despatch the first order that they often do not wait until a contract has been returned and afterwards do not bother to complete the formalities. Anyone in debt to a catalogue company should first write to them and ask for a copy of the signed contract, the company will twist and turn, but in reality if it does not exist there is little that can be done. To be right in law is helpful but if the goods have been received you may feel there is a moral duty to make payment, I would not disagree with this view.