After having successfully paired your ZeWatch3 to your phone you can use the call functions :
Answer an incoming call :
Press the RIGHT button.
Reject an incoming call :
Press the LEFT button.
Disable the ring from an incoming call :
Double tap on ZeWatch3's touch screen.
End current call :
Press the LEFT button
Redial the last number :
Press 2 times the LEFT button.
Control the volume during a call :
Double tap the touch screen then press the LEFT button to decrease the volume and the RIGHT button to increase it.