If you click on the phone icon and nothing happens (or the wrong program opens) your default program is probably wrong. You can adapt this in the Windows Settings.
The fastest and easiest way to go to the right screen is by pressing Windows+s and typing 'default'. Click on the desktop app 'Default apps'. Choose 'by protocol' at the bottom.
The settings-window opens and you can see the default program that is currently associated with the TEL protocol. Click this to choose another default program.