A somewhat different take on the use of callsigns, would I be correct in thinking that anyone who uses a callsign, which they are not entitled to use, to get what they see as preferential treatment from ATC, is breaking the law, or, at the very least contravening CAA regulations? The preferential treatment being because ATC would assume the person calling was an off-duty airline pilot. I am curious as when I was still learning prior to my PPL (I consider I am still learning), I was told that someone, not a BA pilot, had "accidentally on purpose", used the BA callsign for this purpose, the conversation with ATC being along the lines of "Tower, Speedbird.... er correction, G-XXXX ....." and that this happened fairly frequently. My own feeling is that both ATC and BA would take a very dim view of such actions.