When you receive an incoming voice call through the Mobile Office app, you can select the preferred audio device for the call. This allows you to switch between your phone's speaker, internal microphone, or a connected Bluetooth device like headphones or earbuds.
When a call starts or is ringing, tap the audio output icon on the call screen.

A pop-up will appear with available audio device options.

Select from:
Once selected, the call will route audio through the chosen device.
Note: Ensure that your bluetooth device is correctly paired and recognized by your Mobile Phone.