Why can't I hear phone calls on my Bluetooth headset vibe P1?

[AC Question]

I have a Lenovo Vibe P1 smartphone (Android version 6.0 software), and a syska (k700) Bluetooth headset. According to the smartphone I am successful in pairing and connecting the two devices. However when I try to answer a phone call using the headset I hear nothing but the smartphone can and does work properly. Am I doing something wrong if so what is it?