Which corded headset will work with Cortelco 2500 phones which has mute and has noise reduction?
You will need a headset and telephone adapter. The adapter has mute functions for the headset as well as providing noise-canceling.
For headsets go to this link: http://eglobal-teck.com/gnHeadsets.html
For telephone adapter go to this link: http://eglobal-teck.com/gnAmps.html#8210