If you've not done so already, try toggling flight mode to ensure your phone hasn't "dropped off" available coverage. Does your phone show 2G coverage instead of 4G?
Use the "check service status" option on https://ee.co.uk/help/mobile-coverage-checker in the first instance, to check for local service outages. The "report a problem" link should be used if no issues are reported but EE users continue to have issues.A loss of coverage will remove the ability to make/receive calls, send/receive texts or use mobile data.
If you're in the UK and have a WiFi connection, you can use WiFi-calling to keep using your phone as normal without needing network coverage.
