This applet is meant to turn your phone volume up and re-call you to make sure you've gotten your escalation call.
If
Incoming phone call from a specific number missed
This Trigger fires every time you miss a phone call on your Android device from a number you specify.
And
Call my device
This action will call your device with the IFTTT app installed and speak a message provided by your Applet.
Discover more time saving integrations for Android Device and Android Phone Call