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
I certainly would not condone such behaviour and doubt if it would actually gain you anything, but if you normally fly an aeroplane with a company callsign it is extremely easy to inadvertently prefix a call with your usual ''company callsign'', then continue with ''correction, G-XX'' then your message. I am as guilty as others of the inadvertent company callsign slip of the tongue