The easiest way is to see if GSM (Global System for Mobile communications) is working is by taking a look at the status bar along the top.
The GSM icon should have blue bars alongside a double arrow icon that changes a blue and green colour.
Why doesn’t my GSM bar have a double arrow icon?
The double arrow icon represents data connection. If you’re not seeing it please go to the Communication menu and enable your Data Upload to Data or Data with Status.
Also, check the APN (Access Point Name) setting.
You can click on APN and enter the APN setting according to your Telecom operator. Please see the below picture. Don’t forget to SAVE the setting after you enter the APN.