Went to the mountains where no service. Since returning, phone continues to jump out of service even after trying restarting and reinstalling SIM card.

Turn your airplane mode ON. After 30 seconds turn it back off, and test your device.

If it doesn't work, try a forced restart of your device:--> Force restart iPhone - Apple Support

If the issue still persists, contact your carrier and ask for a spare SIM card, and/or for carrier's update (if needed).

No luck? Reset your network settings, going to Settings>General>Reset>Reset Network Settings, keeping in mind that this procedure also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before, but NO other data is affected.

If your network still doesn't work, have your device inspected at an Apple Store or Authorized Serrvice Provider among this list:--> Apple – Location Selector

Regards

Giulio

Thanks Giulio,

I had the same problem...worked for me

Regards Jan

Glad it helped, Jan.

Giulio