I can see why the Contact Centre said this, but I don't believe it to be correct in operational terms, and that is based on the many previous reports in this thread, plus my knowledge of ticketing and gate procedures, I can't see how the other travelling passenger can be blocked. Naturally this is a risk of sorts, but probably only a serious risk if you call up (and even then I have my doubts). Much of BA's operations have been automated, both on ticketing and payment (that's the voucher side). So despite what you have been told, I think Stifle is correct.