Currently when you use the +Call in open activities it opens the create call form.  The form has call results there.

When you click start calling it closes that form and opens the phonebridge popup.  When you click done the call ends and logs under closed activities, but there isn't an option to add the call result.

It doesn't make sense to complete the call result before the call is made.

How do you add a call result after the call is actually made?