That's what I originally thought, but FT made me second guess myself (also, I think I phrased it in a way that could have been misinterpreted).

In the case of the OP, perhaps terminology was the confusing issue for the phone agent. Had s/he instead said "I want to make a reservation for X and I'll pay for it within three days, per the fare rules" I wonder if that would have been dealt with differently...