I just bought a redmi note 7 pro (4GB   64GB, Space Black).
Very often, it happens that instead of ringing( or vibrating in vibrate mode)  I am just receiving missed call notification.

It vibrates momentarily, shows a missed call notification showing how many times phone rang.
The display won't wake either. I know that the phone rang because the person who called told me so.
Now all of this is not to say I am not receiving any call, sometimes it works perfectly sometimes it doesn't.
It's not like it works for some contacts and doesn't for others. It's random like that.
Now my question is, could it be that it is a network issue and not related with phone? Could it be that phone is just alerting me to the fact there was a missed call when phone wasn't connected to network, but the question remains why does the other person hear it ringing when the phone wasn't even connected. I am using airtel 4G VoLTE enabled network in Bangalore. In our area, we do have poor internet speeds but call quality is fine and call drops are rare.