Unfortunately if you are at the airport there isn't much you can do other than to hold. Because it's an Avios issue (presumably) then it has to be cleared by BAEC rather than conventional ticketing.

The advice here (see "Why Can't I check in online?" in the Dashboard) is that if you make a change to an existing reservation it is important for it to be ticketed before OLCI. If it is not possible to OLCI then you have to call in immediately.