iPhone vs Pilot PA86A-BT Bluetooth Cell Phone Adapter

[Gyronaut]

I have an iPhone 4 and a Pilot PA86A-BT Bluetooth Cell Phone Adapter that I can't seem to get to work.

They 'pair' ok and the phone sees a "Movon Bluetooth Device,
When I make a call it asks me if I want to use the Bluetooth device, and I can hear the call in the headset but no audio goes out when someone answers on the other side.

Any ideas from someone who may have had success with this combination please?

Len