This seems quite trivial. According to the help, all you do is:
Invoke OS
Execute on Client
'tel:050-1234567'
Then you get the OS dialog, call 050-1234567 with a Call / Cancel option. Tapping Call, makes the call for you, but I'm the Magic client, when you tap cancel, you get an error message "Error executing command". How can I trap that erroneous message?
Regards
Lawrence
Author of the award winning book, "Kill Me Now!", amusing stories from the world of dating