Had this sort of thing myself just after computer rostering and flight plans first became the norm in the eighties.
Checked into the crew room expecting to go to AGP from my roster, and was given the paper work by ops for AGP.
As the passengers were loading we called ground for the clearance, and was given one to Alicante. No says I, AGP, wrong says the man on clearance delivery, your flight plan is Alicante.
Solved it easy enough by going into the cabin and asking a bunch of passengers where they wanted to go, and it was Alicante, so that is where we ended up!!