I would advise you to open one and then use it to lodge your complaint. Compnsation in Avios is invariably far more generous than the cash offered. Same the other way around with AA, incidently. I got 5000 miles from AA for the armrest on my domestic F flight not working. My BA number was in the booking but I gave the FA my AA number specifically for that purpose. The miles were on the account by the time we landed.