To force Android phones to check for system updates, follow the below trick:
1. Dial *#*#checkin#*#* from your Android phone. Make sure to replace the dialpad numbers with the letters.
2. If there are any updates, your device will show
3. Install the update.
Alternatively, you can also go to Settings –> About Phone –> Check for System updates.
But sometimes, this procedure fails. So, you can always go with the dial method that I explained above.