Like most consumer communication apps, Teams for your personal life relies on your phone number to find and connect to your friends and family. Adding a phone number to your Microsoft account allows you to find others already on Teams. It also adds an extra layer of security to your Microsoft account.
When signing in to Teams with your personal Microsoft account, you need to have a phone number as a sign-in alias on that account. There can be only one phone number as a sign-in alias because when you sign in with a phone number, we need to know which account it's for.
If you get asked to add a phone number to your Microsoft account when signing in to Teams, you need to:
Make sure the correct country is selected in the dropdown menu.
Type your full phone number without the country code and tap Next.
You will receive a text message with a verification code, type it in and tap Next.
If the phone number is not already an alias on another Microsoft account, it will be added to your Microsoft account as an alias and you can use it to sign in to your account going forward.