The main volume controls are on both sides of the T-Max sip-phone, the right side being the speaker and the left side being the microphone. If you are still having troubles, you may have a mute button on your headset, or if your headset is blue tooth, it may be dead or not connected properly. If you do not hear anything, make sure the soft phone is being recognized. Open the soft phone again and click "menu" then "settings", scroll down on the ring device, speaker and microphone and select the appropriate headset. If no specific headsets appear, you may need to have it set on default or the headset is not being recognized at all and needs a forced restart to see the headset. Test the soft phone again, if nothing happens, unplug the headset, plug back in and restart your computer. Restarting often forces the computer to check the headset that is plugged in and will then recognize it. Log back on and test soft phone again, If still nothing happens, open soft phone press "menu" then "settings" and select the appropriate headset for your ring device, speaker and microphone.