iPhone X doesn't switch from WiFi to Data

When I leave my home or office and go off WiFi, my iPhone X doesn't switch to data though the data is on. It shows 4G, and some data comes through, but half the apps don't really update.

I have to toggle data from ON-OFF-ON or Airplane mode from OFF-ON-OFF after which it works normally.

I have automatic network selection enabled, roaming enabled and it seems to work the same way regardless of low power mode.

I am using Airtel in India.