Cannot make a phone call
Cannot make a phone call.
Some smartphones and phone apps do not support hands-free calls.
Cannot hear the caller’s voice.
If the call came while you were listening to music with the headphones, press the 
button to switch to call mode. link
Check that the power of the Bluetooth device is on and the Bluetooth function is enabled.
Select HSP or HFP as the Bluetooth connection profile on the transmitting Bluetooth device. For details, see the Owner’s Manual of the Bluetooth device.
Check that the Bluetooth device is set to handle calls through the headphones. For details, see the Owner’s Manual of the Bluetooth device.
Increase the incoming call volume. link