Text your lost phone, set it's volume to 100% and VoIP call it. -

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When someone sends you a text with the word 'findphone', it sets the ringtone volume to 100% and sends a VoIP call. If someone has your phone, it prompts them to call the number that sent the text saying they found it.

This Trigger fires every time you receive an SMS on your Android device that matches a search you specify.

This Action will set the ringtone volume of your Android device.

This action will call your device with the IFTTT app installed and speak a message provided by your Applet.