If your department is not using Microsoft Teams, you can disable it from your start up after you've logged into it once.
At some point we will fully retire Skype for Business and migrate over to Teams, and at that point we will let you know.
But in the meantime if it's annoying you, feel free to disable it from running at startup.
Right-click on the Teams icon in the system tray, choose Settings.
Uncheck Auto-start application
Right-click on the icon in the system tray again, choose Quit.