You can configure your smartphone to automatically increase the ringtone volume level when you receive an incoming call whose calling party number is on the VIP list.

It is very useful for those who want to receive calls from important persons.

If you set your phone ringtone to small or set it to vibrate, temporarily ring the ringtone.
However, this does not work if the ring tone is set to silent mode by the user.

Warning
This app only supports android 8.1 and below !!!

Reference
You can use the "Missed call alert" app for missed call alerts.