Sync problem with incoming call between iPhone 6 & iPad Air

Sync problem with incoming call between iPhone 6 & iPad Air

I am using iPad Air (WiFi-only version, no SIM Card) & iPhone 6 in Dhaka, Bangladesh. When both my Devices were in the same WiFi zone, e.g. inside my home, if a voice call came to my iPhone, both my devices rang and thus I had the option to receive the call in my iPhone as well as in my iPad and continue talking using loudspeaker.