Have I made a mistake?  Or, more to the point, has a salesman mislead me?

I want to use my computer as a PA system for demonstration purposes.  I was
told if I buy a Bluetooth Headset and a Bluetooth USB adaptor I could use
them to speak through my speakers and be hands free for my demonstrations.
I have Logitech Z-649 speakers.   All this on the recommendation of a
Bluetooth salesman.  Sadly - they never reply to their 'support' e-mail and
there are no technicians available locally to help.

I can't get it to work at all.  The headset shows as being connected in that
it blinks blue three times.  When I go into the Bluetooth 'Places' it shows
the headset as being 'Not connected'.

Have I wasted my money?

Alternately how can I gat an ordinary wired headset to act as a PA system?

TIA