Practical answer
What happens to iMessage when I switch?
Deregister iMessage before you stop using your iPhone, or texts from iPhone users will vanish into it.
If your number is still registered with iMessage and you move it to a non-Apple device, messages from iPhone users can be sent as iMessages that never arrive. It looks like people are ignoring you.
How to avoid it
- On the iPhone, before you switch: Settings, Messages, turn iMessage off.
- Also turn off FaceTime for that number.
- If the iPhone is already gone, Apple provides a deregistration page where you enter your number and confirm by code.
Do this on the day you switch, not a week later.