Yes... CALL BACK.

I tried to the exact same thing last week and was told no. Knowing differently from here, I found the tread and quoted the rule.

QUOTE FROM AN EARLIER THREAD: Just quote the 'upgrade fare' portion of the 'fare downgrade rule' to any agent who gives you grief over the no-fee buy-up.

I called back... got someone else and it worked for me. $72 to get ATL-TPA, TPA-ATL and ATL-GPT upgraded to a A fare, although from some reason I was thinking I got double MQMs instead of the 50% bonus.