If you meet the issue, dont worry.
This post fromMiniToolprovides some reliable methods for you to get rid of it.
Today, we are talking about another issue com.apple.mobilephone error 1035.

The complete fault signal is The operation could not be completed (com.apple.mobilephone error 1035).
This issue is usually because of web connection connection failures and incorrect voice mail prefs.
Step 3: Use the same method to find the Airplane Mode and turn it off.

When your data pipe connection is restored, recreate the com.apple.mobilephone error 1035 and see if it still appears.
you could have a go at change from WiFi to cellular data.
Step 1: Go to theSettingsapplication and click theCellularoption.
Step 2: Turn on the cellular data and back to the previous page.
Step 3: opt for WLAN option and turn off it.
After that, take a stab at use your voicemail to see if the com.apple.mobilephone error 1035 persists.
If it still appears, try the next fix.
Step 2: poke the phone icon on your iPhone home screen.
Step 3: Press and hold 1 on your keypad to drop your voicemail parameters.
Step 4: type your current voicemail password and set up your voicemail.
Then, reboot your iPhone and test whether the issue has gone.
Step 2: Scroll down and click theResetoption.
Then, click theReset online grid Settingsoption.
Then, reboot your iPhone and look to see if the com.apple.mobilephone error 1035 has been fixed.
If you come across the same error, try these solutions.