The iPhone XS and XS Max are barely one month old, yet both have a serious problem in Messages. When sending a friend an SMS/MMS text rather than an iMessage, the phrase "Number changed to Primary" appears in front of each and every message. What gives? If this issue is driving you mad, there are a few tricks that may exterminate the bug until Apple gets around to issuing a patch.
First of all, astute observers or those complaining to friends will see this is only affecting iPhone XS and XS Max models. All other models, including the iPhone 8, 8 Plus, and X, remain immune to this annoying message. Why just the XS and XS Max?
This bug is somehow caused by the dual-SIM capabilities of the XS and XS Max. Since the iPhone XR has the same tech, it will be affected as well. Apple touted dual-SIM support during its September 2018 presentation, but dual-SIM functionality isn't working until iOS 12.1, which, as of now, has no official release date.
We've seen reports that resetting iMessage and FaceTime settings can solve the "Number changed to Primary" issue, even though this problem is occurring exclusively with non-iMessage text messages. Still, it's worth a shot.
To reset iMessage, jump over to "Messages" in the Settings, then tap the toggle next to "iMessage" so that it's off. To reset FaceTime, go to "FaceTime" in the Settings, then tap the toggle next to "FaceTime" so that it's off. Next, wait for 30–60 seconds, then enable both toggles again.
Now, go back to your non-iMessage chat, and send another message. If you continue to receive the "Number changed to Primary" statement, move onto the next possible fix below.
Your iPhone is really just a computer. Sometimes, computers get jammed up and need to power cycle to solve issues. It's not likely, but try a soft reset on your iPhone, i.e., power down and then back up, to see if your problem goes away.
This part's never fun; When you have a bug that won't shake itself loose, performing a hard reset (aka force restart) on your iPhone is a solemn but necessary nuclear option. This reset will wipe all data from your iPhone — photos, messages, notes, and anything and everything you do on your device. If you want to proceed, make sure you have all important data backed up. Anything not saved will be lost after the restore.
We recommend you keep all app data you can tied to iCloud since, to truly ensure your iPhone's software is responsible for the bug, you're not going to want to restore your iPhone to a previous backup. Having your data stuck to iCloud means, once you sign into your iCloud account on your restored iPhone, your data will come back.
You can make sure your data is saved to iCloud by going to Settings, tapping on your name at the top of the display, select "iCloud," then ensure all relevant data is enabled under the Apps Using iCloud section.
To completely reset your iPhone, open Settings, tap "General," then scroll down and tap "Reset." Here, select "Erase All Content and Settings." If your iPhone hasn't been backed up recently, you might get a reminder to back up. To keep going, tap "Erase Now," enter your passcode, then tap "Erase iPhone" when prompted.
Let your iPhone completely erase. When it boots up again, go through the initial setup, but again, make sure to select "Set Up as New" when prompted. That way, you can ensure that if the problem is related to your iPhone's software, it won't be present. Now, if you still encounter the bug, you can:
Dual-SIM functionality is coming to iPhone XS and iPhone XS Max as an update in iOS 12.1. While there's no official release date for 12.1, the software is currently available for beta testing for any iPhone owner who wants to opt-in. If you want to see if the beta solves your issues, give it a shot.
If you don't see results from any of the tips above, you might have to wait until Apple officially releases iOS 12.1. It's frustrating, but in the meantime, just tell your friends with Android devices you simply can't text message them for a while.