How to make a phone call in "native" Xamarin.Forms in Windows Phone...?

To XF, there is an example to make phone-calls over uri:

Device.OpenUri(new Uri("tel:012345-33-32"));

In the example, for WP an alert is shown ("not yet implemented" or similar).

This works on iOS and Andorid, but not on Windows Phone.

Question:
How to make a phone call in WP (similar to the example above)?
Thanks