Originally Posted by
debug
Thanks for the quick reply both.
Yes, it was online. I did call to double-check as the $3500 change seemed a lot.
Ticketed Wed, Jun 01, 2022. Outbound travel Thu, Jun 09, 2022, fare rule TFFD4 . Inbound Fri, Jun 10, 2022. Inbound was subsequently changed to Wed, Jun 15, 2022 (For $0 in change fees), fare rule UKXFFB3.
OK, TFFD4 does allow a double-open-jaw combination, so that's not the problem.
I actually don't see a T fare that would cover an immediate return. TFFD4 requires a four-day minimum stay, which matches your new schedule but not your original schedule. So that's a bit confusing.
That said, I see U inventory from ORD to LHR on all three nonstops, and the LON-CHI U fare appears to combine with the TFFD4 outbound fare just fine. In fact, I see a fare difference of about -€70, give or take.
I don't see any reason that this would have to be re-priced as a very expensive fare (the $3000 fare difference suggests that they were repricing in unrestricted Y), and I'd probably call and try again. Perhaps a different agent will compute the price differently -- or maybe inventory has just opened up in the last couple of hours.