[boba6421]

Is the ring volume turned up? If you tap on the speaker icon in the task bar at the top. Is the volume slider on the right turned up?

I do this while at work when listening to music. I have the sounds on so i get them through my headset, but have the ringer off so it doesn't ring through the speaker.

Also go into your Sounds and Notifications settings and verify that the Incoming call event ring type is not set to 'none'.