The pie box has a tick on the side saying what kind of pie it is. If the pie turns out not to be what it says on the box take it back. It'll clearly have fork/teeth marks in it because how else are you going to tell what the contents are without trying it? If they won't change it or give you a refund, speak to the manager. Mentioning trading standards should do the trick. Clearly its the catering company's mistake and they need to put it right. After they've had to throw away a number of mis-sold pies they should finally twig that its denting their profits.
Boxes don't appear to be ticked. Bpought one of each on Monday. All piping hot. All excellent. But working out what was what required a bite!