No text, I can't send or receive calls.
Sounds like something is out of whack or the sim is damaged. Let's do the following:
Settings> General> Reset and choose reset network settings.
Give it a few minutes to redetect everything...then try to make a call.
When I go to Settings>Phone>My Number it shows my phone number. Does that mean I do have my own sim back?
I did try resetting. No change. Now when he handed my phone back I got two texts that were meant for him. What does that mean?
that means you have his sim. If you got texts that were meant for him on your phone, then you do have his sim. If you have his sim and he cancelled his service, then that would explain why you can't do anything with it.