Reprogram your phone to select Intercom before the lines.
When your phone rings, just press ON. It will connect to the ringing line.
If you want to call another extension, press ON to get Intercom dial tone, then dial the other extension, or 777 for voice mail, etc.
For outgoing calls, press 9 to get outside dial tone, then the telephone number.
To transfer, press Flash, then the extension number you want to send the call to. Either hang up to complete the transfer, or wait for the other party to answer, announce the call, then hang up to complete the transfer.
To hold a call, flash and dial your own extension number. To pick it back up, dial 6 and your own extension number.
If you hear an announcement that a call is holding for you, and which line it is on, press 6, 8, and the line number (01 for line 1, 02 for line 2, etc.)