If you call other internal or external people often from your Teams Phone, you may want to consider adding them to your Speed Dial/Favorites for quicker access to calling them.
The easiest way to add people to this list is from the Teams App on your computer.
In the Teams App, go to the Calls tab, then you will see Speed dial in the top right-hand corner. Click the small icon to add to your Speed dial. It can contain both internal and external contacts.
Once you add contacts to this Speed dial in the Teams App, they will also show up in Favorites on the Teams Desktop Phone as well, allowing 2-tap access to calling those you call the most often, by tapping Calls and the person you want to call.