use my sim card in his? and he can in mine?

with nothing coming up

The reason for that is that Rogers bought out Fido 2 years ago, therefore the SIM cards use the same programming, but just with slightly different names attached to the service. Incidentally, the reason for SIM cards is supposed to be so it's easier to change phones, but they have been known to charge you about $200 if the card gets fried, even if you only fell and it landed in a puddle.