I have had all manner of BS excuses on RTW and 241 bookings. The key always is to ask them to show you where EXACTLY in the fare rules does it state what ever they want to try and convince you of.

I've had the same 72 hour rule thrust upon me and they tried to tell me it was an unpublished rule which is just laughable. Perhaps mention "unfair contract law" etc etc In my case they relented otherwise it would be a free for all.

As far as I am concerned if it is not in the fare rules or the T and C's then it is not valid - so just ask them to prove it