readme: mention systemctl for stopping calls

README.md

@@ -44,9 +44,7 @@ run script which sets up the environment for you:
 
 *Note:* Invoking the run script might terminate after a few seconds and
 instead only activates an already running instance of `gnome-calls`.
-In this case you want to `killall gnome-calls` until it says `process not found`
-(you have to kill more than once because the process might automatically get restarted)
-and only then use the run script.
+In this case you want to `systemctl --user stop calls` to stop it.
 
 ### Debugging