Turn off your iMessages on your Apple device
1If you paired an Apple Watch with your device, unpair it.
2Back up your Apple device
3Put the SIM card you transferred back into your Apple device.
4Make sure you’re connected to your operator's mobile data network (such as 3G or LTE).
5Tap Settings → Messages and turn off iMessage.
6Tap Settings → FaceTime and turn off FaceTime.
If you don't have your Apple device or can't turn off iMessage
After you deregister, text messaging should function as expected instantly, however in some cases this may take up to a few hours.
If you have other Apple devices, iMessages to your Apple ID will still be received by devices that have iMessage enabled.
*iMessage and iPhone is a trademark of Apple Inc., registered in the U.S. and the other countries.