When my missus changed her last name on her passport we faxed the new photo page over to the ba executive club (having called first) and they just changed the name on all her future flights. That is apart from the first one which they forgot about and this resulted in some measure of chaos at the ticketing desk at lhr. They wanted to charge a change fee; a call to the baec solved that in short order. If it's relevant our baec is based in the usa.