Receive incoming calls in Android 6?

This pertains to VOIP calling- quoting from Motorola site

Motorola VoIP and SIP client apps enables customers to make free phone calls to other VoIponMobile users or very cheap phone calls to anyone else in the world from your Motorola mobile phone.

If you have access to a WiFi, 3G or Edge connection, you can save money by using the Internet to connect your call instead of using your mobile minutes. No roaming or out-of-network fees. Make your calls from anywhere in the world to anywhere for just a few pennies a minute. Simple to configure, inexpensive to use

Enabling incoming calls would make you get incoming VOIP calls, provided your carrier permits that ( AFAIK Airtel doesn't)