This can happen if you used iMessage on your iPhone and then transferred your SIM card or phone number to a non-Apple phone (like an Android, Windows, or BlackBerry phone). If you didn't turn off or deactivate iMessage before switching to a non-Apple phone, other iOS devices will still try to use iMessage to send text messages to your phone number.
If you're not getting SMS or text messages from someone with an iPhone, or you can't send SMS or text messages to someone who used to have an iPhone, learn what to do.
If you still have your iPhone
- Put the SIM card you transferred from your iPhone back into your iPhone.
- Make sure that you're connected to a cellular data network (such as 3G or LTE).
- Tap Settings > Messages and turn off iMessage.
- Tap Settings > FaceTime and turn off FaceTime.
If you don't have your iPhone or can't turn off iMessage
These steps won't deregister your phone number with iMessage:
- Logging in to My Support Profile and changing your password or removing your phone number
- Texting STOP to 48369
- Resetting your network settings
- Changing your Apple ID password