Originally Posted by Calchas

BA won't change your ticketed points (the cities on your ticket) unless you are really insistent that this is the only acceptable option to you.

On the other hand you may be able to evade some other fare rule provisions, such as creating a stopover at IAD or forcing availability in a sold-out fare bucket.

It's always best to have a good idea of what you will or will not accept, and if you need time to think, ask the agent to annotate the PNR with your conversation and say you will get back to them.