Was looking to Upfare a 'Standard' fare purchased on my behalf online... When I got to the payment screen, a "Change Fee" of $105.00 was added. No change in any flight on the itinerary. Called reservations - same answer. Prodding re: same flights but moving up in "fare family" only, but agent repeated change fee. Asked nicely again, pointed out that it hasn't been problem in the past; questioned if a possible change in the available bucket within the family was the issue... Long story short, I think she messaged a supervisor on the side and had any extra fees waived "as a one-time option." Does lack of availability in a particular bucket negate the "free" upfare to a higher family (i.e. all 'T' is gone so, when moving from Standard 'T' to Comfort 'T' you actually get Comfort 'G' and the system sees it as a "true" change)?