What to do if there is a cellular issue detected on my iphone??

Contact Apple Support if one of these messages appears on your iPhone or iPad:

• Cellular Issue Detected
• Ultra Wideband Issue Detected
• Apple Pay Issue Detected

You might see these messages on the Home Screen or in Settings > General > About under Parts and Service History.

If you want to try more steps on your own

You need a computer to follow these steps.

1. Make sure that you have a backup of your iPhone or iPad.
2. Connect your device to a computer that has the latest version of macOS or iTunes. On a Mac with macOS Catalina or later, open a Finder window. On a Mac with macOS Mojave or earlier, or on a Windows PC, open iTunes.
3. If "Trust this Computer" appears, unlock your device, then tap Trust.
4. Select your device.
5. In the Finder, click General. Or in iTunes, click Summary. Then:

• • On a Mac: Command-click Check for Update.
  • On a Windows computer: Control-click Check for Update.

6.Click Download and Update. Continue by following the onscreen instructions.

Your computer will download and reinstall the current version of software on your device. Don't disconnect your device from your computer until the download completes.

If the message still appears, contact Apple Support.

Kinagatna ~ A weak battery can cause a "Cellular Issue Detected" message. And if the replacement battery is not a genuine iPhone battery, the maximum capacity % may be stuck at that false 99% value. So the battery health could actually be much lower and causing the "Cellular Issue". Here's a similar situation to yours, but with the capacity stuck at 80%:

I can’t use my cellular data what’s wrong - ASC

...So I suggest you ask your friend about the battery: Was it changed by a qualified technician using a genuine iPhone battery?...

About genuine iPhone batteries

Repair Provider Verification

(Articles found by searching Apple's Knowledge Base.)

õ¿õ¬

KinagatnaMansanas wrote: "yes,.still the original battery with 99% health"

An iPhone 7 original battery is very unlikely to have a maximum capacity of 99%. Please confirm that 99% is the Maximum Capacity from here:

Settings > Battery > Battery Health

õ¿õ¬

Kinagatna ~ Does your iPhone 7 still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

õ¿õ¬