Thanks to both. FINALLY got through to the e-service center. (My third try, with hold time to an agent ~20 minutes. Gave up after 30 minutes the prior two times.)
Not surprising; the change is prohibitively expensive due to restricted ticket. The e-service rep was very helpful.
Just boggled that if I DID want to give CX the up-fare $$, they make it that difficult.
But, now I know. Appreciate the FT help as usual.