Konftel 55Wx works best when connected over USB to a PC.
This will also charge the unit and has the most stable connection. 
Bluetooth functionality is mainly to be used when connecting to mobile phones (which works really good). 
We recommend USB over Bluetooth for PC, because of is poor compatibility in both Bluetooth hardware and software in Windows OS, especially when connecting to Bluetooth headset.

Using the Bluetooth voice compatibility mode setting on Konftel 55Wx can in many cases solve issues in Windows. 

Access it by going to Settings (cogwheel) and long-pressing on the System button for 4-5 seconds and Enable Bluetooth voice compatibility mode.

We have realized that we have customers that also want to be able to connect Konftel 55Wx to PC over Bluetooth. 
To solve this we have developed a USB Bluetooth dongle, Konftel BT30 

Konftel BT30 was designed for Konftel 70 and 800 but it will work with the Konftel 55Wx as well. 

Konftel 55Wx does not support Bluetooth Class 1 so the range will not be as good as for the Konftel 70 and 800.