Apple iMessage only works with an Apple id and your iPhone mobile number. Since SMS activation is only required if you want to use your phone number with iMessage / Facetime chat, removing your phone from iMessage should stop the request for repeated SMS activation.
To remove your phone number from iMessage follow these steps:
On your iPhone, go to Settings > Messages > Send & Receive. Select your Apple ID and tap
Then go to Settings > FaceTime, select your Apple ID and tap
Additionally, some may require to go back to Settings > Messages > Send & Receive and Tap “
Use your Apple ID for iMessage” and sign in with your Apple ID.
(Note: If Messages and / or Facetime section in settings is disabled / greyed out, go to Settings > Screen Time > Content & Privacy Restrictions > Account Changes and tap '
Source: Add or remove your phone number in Messages or FaceTime on all your iDevices and Mac.
ºº(This didn't work for me on an old iPhone with an outdated version of ios and still kept asking for SMS activation. So update ios on your device if you still have issues.)
Yeah, this is an issue with iMessage / Facetime and I would even label it a bug, even if Apple doesn't consider it so.
In fact, it's even more irritating for users like me who have to pay international rates for the SMS that iMessage / Facetime wants to send to Apple for activation.
This is an Apple issue and not a carrier / cellular phone provider as this is about activation of an Apple service (iMessage / Facetime). So talking to your carrier support won't help with this.
Before you can use iMessage / Facetime chatting service on your iPhone, it requires that an SMS be sent from your phone to Apple to activate it. This SMS is sent the first time you try to use iMessage / Facetime or if ios thinks your iMessage needs to be activated. So for me, and many others outside US, it sends a costly international SMS to Apple.
This SMS activation is required if you want someone to also be able to iMessage you using your mobile phone number. (Note that by iMessage I mean message that is sent through iCloud and internet and not SMS, which are messages sent through your carrier network. You can always send SMS through the Message app without requiring any such Apple activiation.).
I presume that iMessage / Facetime keeps asking to send SMS activation on every restart, because it probably wants to verify if you have changed your SIM card or phone number.
There is currently no known method to avoid sending this SMS to activate iMessage on the iPhone. (Apple iPad and iPod Touch don't require SMS activation for using iMessage as you can only use your apple id for iMessage on these devices).
The only way to avoid paying the SMS charges is to change your plan to one that includes free SMS (but this option will work only for US citizens, as no plan I've heard of includes free international SMS!). Or to a different carrier that has an understanding with Apple to not charge for such SMS sent to Apple. (Yeah, I know both options suck).
Note: If you frequently have to restart your iPhone because the phone seems to hang or struggle, it may be time to change your iPhone's battery. As your battery becomes older, ios throttles your phone so that the battery is not strained and can give you longer battery life. But ofcourse, this means that your phone becomes slower and everything feels sluggish.iPhone's
More information on this can be found here -
- iPhone Battery and Performance
- What is iPhone throttling and why does it happen?