If someone, or some fax machine won't stop calling you, you can use your Mitel Connect app to create a routing rule and the system will automatically hang up on them.
Within Mitel Connect's settings menu, configure your call routing as such:
(Click your name and then the settings gear)
Give the rule a meaningful name so you can tell them apart should you add more later:
Specify the Hang Up auto attendant as to location to forward the call to: