If OP PMs me the city pair, fare basis, travel dates, and ticket purchase date, I can send along a full copy of the fare rules from ExpertFlyer, which might find some sort of loophole that will allow cancellation with residual value as a credit or something like that. I'd not encountered such fares ex-LHR (although there are reports of them being common ex-continental Europe), so there may be some portion of the fare rules that could help that the phone agents have been missing.