Go to the Main Menu > Phone > Phone to open the virtual numeric keyboard.

Do the following;

- 1 click up on jog dial and press (*)
- 2 clicks down on jog dial and press (*)
- 1 click down on jog dial and press (*)

to open the hidden Service Menus part of the phone.

Then go to the Service Tests > Speakers.

There are two selections, rear and front, and the "front" adjusts the volume of the ear speaker, which is used during the calls. Increase the volume to %100. Quit the Service Menus and make your call. I made one try and it was cool!