Have you used the headset feature code to enable the headset properly?
As far as I know the speaker key becomes the clear key on the 5000 so transfer then the speaker key.
If it is a 3300 you may need to program a release key.
To get the headset working, I've had to go on the System Administration Tool and add the headset into the User and Device configuration section (I googled it and found a post on this forum about it).
I've tried pressing the speaker button but that doesn't seem to have any effect.
How do you hang up when completing a normal call?
With the headset in, we press the 'cancel' key and that disconnects the call. When trying that to transfer the call, it doesn't pass it over to the other person it just lets you speak to the person you were trying to transfer in the first place.
Chris is correct, to answer the call you would press the Speaker Phone button, press transfer and dial the number, press Speaker Phone again to transfer the call to the other party.
I've tried pressing the speaker button, but it doesn't seem to answer the call or transfer it