A friend was asked the same. The agent said that if they actually get the tickets printed, the airline can't ask for more cash. If the tickets hadn't yet been printed, even if the flight had been paid for they could ask for more. Something like that anyway.
Got a call this morning as well, need a new card, current one void as of today. I know what you mean oblivion about them not getting to the point. When she first talked it sounded to me like there was an option, but there wasn't.
If I'm buying a ticket and looking for a deal, I won't let these air mile cards cloud my judgement - they are often increasing useless as people above have said.
Are there any airlines out there that have not clamped down on all this?