How do I increase the speaker volume on HTC One VX phone calls?

[chayes418]

Phone calls are often hard for me to hear using my HTC One VX. Can the speakers' volume be increased?

 

[Phillip Corcoran]

Incoming voice volume can be increased or decreased, but only when a call has been accepted and the caller starts to speak.
Press the volume up/down button on the right-hand edge of the phone.
Press it in at the top to increase the voice volume, or in at the bottom to decrease.
The volume level stays where you set it for all future calls until you adjust it again.