014 ticket with A3 flight connecting to AC booked in Y with AC segment confirmed R. A3 delays flight but never posts an official delay so AC can't touch ticket. Eventually, as flight is enroute, A3 sends notification of rebooking via BA in Y with new ticket stock 390 (A3). AC concierge says she can't touch ticket so eventually I got A3 to switch from BA to later AC flight but only in Y because A3 says it does not recognize R class. AC refused to confirm seat in R/J, which was J8 R0, though upgrade did eventually clear wl at the gate. Was this handled correctly by AC?