As far we know, recent Apple iOS update 12.1.2 is going from bad to worse for iPhone owner. From loss internet connection via cellular, until totally cellular network blackout. If you already backup your iPhone using cloud backup service, it should be no problem regarding your data. But, if you already update it before backing up your data, here is instruction how to fix it :
How to fix : can’t connect to your cellular network
Unfortunately, it’s unclear if this was addressed in iOS 12.1.2, and there’s no real ‘fix’ beyond reverting to an older version of iOS (12.1, essentially). To do so, you may have to connect your device to a computer, navigate through iTunes to device settings and restore from there.
How to fix : Your iMessages are sent to the wrong people
An odd issue after updating to iOS 12.1.2, someone reported that their iMessages are being sent to the wrong people. If that’s the case, there might be an easy solution: switch to Family Sharing, which creates separate contacts, calendars, notifications and so on. Another forum user suggested something a bit more laborious. Those using the same Apple ID must go into each of their device’s iMessage settings and decouple it from their Apple ID. Make sure they only have phone numbers or emails in the Contacts entry for whomever else is using the same Apple ID, and messages shouldn’t be jumbled up between them anymore.
How to fix : Trouble with eSIM on iPhone XR, XS and XS Max
Some iPhone user encountered bugs activating eSIMs in their iPhone XR, XS and XS Max phones, good news is the iOS 12.1.2 update has a fix. Apple didn’t release too much detail in its notes for the new version of iOS, so hopefully this fixes the particular eSIM issue you were experiencing.
How to fix : iPhone XS won’t charge
You may have experienced your iPhone not charger when it’s plugged in and asleep when you put the Lightning cable into the phone. The temporary fix is to make sure you plug in your phone when it’s lit and you hear the charging chime and see the visual charging cue.
How to fix : Increased battery drain
First, check your device battery’s health to ensure that’s not causing the drain. If the maximum capacity is below 85%, it may be time for a battery change. In this case, it’s a hardware issue.
Second, if it’s a software issue, this new iOS 12.1.2 for iPhone problem might actually be caused by an old problem we’ve seen before in the last grand update to iOS 11. The internal reorganization temporarily taxes iOS devices and drains things faster.
Hopefully, latest iOS update from Apple will resolve all of this issue, but to protect your data, make sure you already have your own backup about your data. If you want backup to do automatically, you can choose cloud backup that offering more flexibility and more security about your data. Make sure that everything in your iPhone already backed up, and then you can update your iOS safely.