Create conference with 2 existing calls

[Mauro]

Hello, I was looking into this stuff too.
With our old T20 and T22, you could press "conference" when you already had two active calls (one of them on hold, actually) and they would have merged in a conference.
With T21PE2 and T43U, if you press "conference" when you already have two active calls, it tries to call a third number... is there a way to just merge the existing calls?

Example:
1. Phone A calls Phone B, B picks-up;
2. Then Phone A holds Phone 2 and makes a new call to Phone C, and C pick-ups his call.
3. Phone A presses "conf" key. The phone asks to type a new number to initiate a conference with yet another phone. Makes sense in case you want to make a 4-way conference I guess, but that's quite unlikely. Is there a way to merge the two calls at this point?