Explainer video for "call back mode"

Hi there, In our company we are about to deploy a new telephony system, which will replace deskphones with softphones on computer. One of the things that is difficult for the people to understand is the notion of prefered device. This means they can choose to receive their call on their private mobile phone for example, but also to make call with their private devices. Let's say John wants to call Sally, using his private mobile phone as prefered device. john should initiate the call from his PC or mobileapp, and his mobile phone will ring. Once John answers, Alice's number is dialed and her device rings. Once she answers, they can communicate. It is quite conterintuitive for the end user that they initiate a call and their device rings. I need an explainer video to explain this to them. Length should be limited (<1min) and format can be whatever I can upload on my project website (mp4 for example). There should be no voice (only text), and the text should be in french (you can make a proposition in english and I'll provide translation). I propose a script but I count on your support to rework it into something that is clear and engaging.