Originally Posted by
LondonElite
You sure can, as Prospero suggests. However, award space needs to be available on that flight. The best way to find out if there is is to try to book a seat in the higher cabin on BA.com using Avios. If there is, call BA to change your ticket.
We're all guessing what the OP is actually asking, but this isn't "upgrading" a ticket, which is the process set forth here,
http://www.britishairways.com/en-us/...ing-with-avios, and cannot be done on award tickets. What Prospero is suggesting is changing your current award ticket to a different award ticket. Perhaps semantics, perhaps not.