Does my phone have to be unlocked to switch to Wing?
It all depends on the carrier you are switching from. Phones from Verizon, AT&T or T-Mobile do not need to be unlocked in order to switch to Wing.
Phones from Sprint and certain others carriers will need to be unlocked in order to join Wing. In these cases, you're responsible for ensuring that the phone is unlocked and compatible.
The best way to know if your phone is unlocked and will be able to switch over to Wing is to reach out to a Wing Agent directly.