How To: Deregister Your Phone Number From iMessage

If you recently moved from an iPhone over to another device, such as an Android or Windows phone, you may find you can no longer receive SMS text messages from your iPhone-using contacts. Here are two ways to fix the issue.

If You Still Have Your iPhone

If you still have possession of your iPhone, follow these steps:

1. Transfer your SIM card to your iPhone.
2. Go to Settings.
3. Tap the “Messages” menu option.
4. Turn iMessage off.

Now, your iPhone should be deregistered from iMessages, and SMS text messages from iPhone-using contacts should come through like they should.

No Longer Have Your iPhone?

If your iPhone isn’t still in your position, there’s still a way to deregister your old handset.

1. Visit the Apple Support Website here: https://selfsolve.apple.com/deregister-imessage.
2. Enter the phone number of the device you want to deregister from iMessage and Apple will send you a confirmation code.
3. Enter the 6-digit code Apple sent to you in the field at the deregister page above to confirm deregistration of your iPhone.

Either of the sets of steps laid out above should deregister your iPhone, and allow you to receive SMS text messages from iPhone users.

Thanks to @TheGlennja for the link.