To Decline An Incoming Call; To Switch To An Incoming/On-Hold Call And Put The Current Call On Hold; To Switch To An Incoming/On-Hold Call And End The Current Call - b&o EARSET 3i Manual

8 To decline an incoming call ...
>
Hold down the centre button for two seconds and let go.
>
Two low beeps confirm that you have declined the call.
To switch to an incoming/on-hold call and put the
current call on hold ...
>
Press the centre button.
> Press again to switch back to the first call.
To switch to an incoming/on-hold call and end the
current call ...
>
Hold down the centre button for two seconds and let go.
>
Two low beeps confirm that you have ended the first call.