How to fix the issue?

This post fromMiniToolprovides some useful methods.

Now, keep on your reading.

Reset Network Settings

Here is how to check it.

Step 1: Open thePhoneapp.

Step 2: Tap theVoicemailtab at the bottom of the screen.

Here are the steps:

Step 1: Turn on the phone.

Step 2: check that you are on the keyboard.

Press and hold the number 1 for a few seconds.

Then, you could check your voicemail here.

Step 3: Use the same method to find the Airplane Mode and turn it off.

you could attempt to change from WiFi to cellular data.

Here are the instructions:

Step 1: Go to theSettingsapplication and click theCellularoption.

Step 2: Turn on the cellular data and back to the previous page.

Step 3: tap the WLAN option and turn off it.

Ensure the toggle is set to off.

Go toSettings > General > Date and Timeand double-check your iPhone is set to the correct time zone.

it’s possible for you to reset the online grid controls by following the steps below.

Step 1: Go to yourSettingsand open theGeneraloption.

Step 2: Scroll down and tap theResetoption.

Then, tap theReset data pipe Settingsoption.

you might do this by logging into your carriers website or by contacting customer service for assistance.

If you come across the same error, try these solutions.