See there are two fixes i can suggest that you can try
Before you proceed make sure your network has activated internet
services for your mobile
1. The quickest way to reboot your internet connectivity is to turn on airplane mode and then turn it off.
2. The fix for the issue should come on the air (OTA), because a lot of people have complained about it, not only this, there's a different issue that as soon as you turn the wi-fi off the network internet does not become active, you should connect to the internet using wi-fi and update your OS.