So I understand correctly, the SYSTEM is putting the call on hold or the OPERATOR is putting the call on hold?? Mine doesn't automatically put a call in progress on hold when a new one comes in, but it will alert you to the call. Unless possibly if you have a headset and you have the auto answer crap configured?? I use headsets, but I do not program the headset key or do any special setup - just hook it up and use the headset key to answer a call or get dial tone.
Assuming you have multiple line appearances on your phone and you are using the hunt group in kind of a "rollover" fashion, which is what I do, here is how I tell my receptionists to do it:
1) You are on a call and another comes in on the next line.
2) DO NOT put the call on hold. Just ask the person you are with if they can hold for a moment, and then Press the Ringing Line Key.
3) The original caller will be placed on "soft hold" and you will be speaking to the second caller.
4) (I suggest) tell the second caller you are just finishing up with another caller and you will be with them shortly - please hold.
5) The menu will have a "toggle" option, or if you have a "Connect" button on your phone, use that to switch back to the first caller.
6) Apologize and finish up the call.
7) There should be a menu option for Return to Held Call (or just toggle again) - use that to grab the second caller now... and etc, etc...
I have not been able (had the time) to determine if it is possible to do this scenario with more than 2 calls at a time. If you can, there must be some way for the phone to ask you which caller you want to pick up when you hit the Togge/Connect.
I may be completely off the mark with what you are trying to do, but I tried...

) I have found that if you are handling a call on your prime line, and then put that call on hold and try to hit the second ringing line you will dump the first caller.
Don Bruechert, Voice Comm Analyst II
CareTech Solutions @ Holy Family Memorial
Manitowoc, WI, USA