Adjusting headset microphone volume

[cocaccro]

Hello, I am using a SIP-T20 phone with a Yealink handsfree headset. The microphone is extremely weak, and often I have people ask me to repeat things or speak up. Sometimes when I am leaving voicemails (holding the microphone right next to my mouth), the machine cuts me off as it doesn't hear me. So I have to append to my messages, which makes for awkward and unprofessional communication.

I have been looking at some threads on this site about how to increase the microphone volume, but all this talk of auto provisioning, etc. has my head spinning.

Could someone please walk me through what I need to do to increase the volume of the headset? What program should I download to do the tftp thing (if that needs to be done), and what exactly needs to be done each step along the way?

Thanks very much, in advance.