It seem such a simple thing but I have all my contacts available on the desktop app but there is then no way to move them all to the phone (apart from doing them all manually one at a time).
The phone has this feature built into it via a Yealink web app but RC say this doesn't work.
Only other suggestion was to call through the app then flip the call once connected, which isn't very good as there would be a big pause while you do it.