I remember you flying your BE36 into BVI on an NGF mission back in 2005. At the time, Pa Am Flight Academy had a pretty large presence there with a fleet of 22 Archers, 2 Seminoles, and a C152. Most of the call signs ended in ***PA. In fact we had a N623PA, N923PA, and N423PA frequently in the pattern at the same time and yes, we were required to use their full call signs.
Pan Am later went to Company Call signs (ie., "PanAm 11, PanAm 4, or PanAm 8-Sierra etc. for solo flights"). That helped with the similar call sign problem but made things more confusing because the call sign had nothing to do with the tail numbers.