House is right. However, even though your contract is with BD, matters such as seat pre-assignments are extra-contractual and the airline can refuse to give you a seat pre-assignment or insist that this is dealt with by the same channel through which the booking was made. There is a tendency among some European airlines to play those silly games. BA and KL have been known to refer customers back to TAs for issues such as seat assignments. I find it rather disappointing that BD should enter the customer dis-service game.