littlepilot,
Don't panic...'cos [sometimes] ATC can't find their callsigns either
FCA/First Choice have a "Numeric" ticketing system....FCA1234 MAN-AGP....
The ATC "Callsign" could be FCA123C......
if we are lucky, but it could also be FCA 964C......c'est la vie
Keeps us ATCers awake though
watp,iktch