i cant add a phone number

The missing phone-number option is expected for some personal Microsoft accounts because Microsoft is phasing out SMS for authentication and account recovery; add a recovery email, Microsoft Authenticator, or a passkey instead.^1^

Add another security method

1. Open your Microsoft account’s Security tab.
2. Select Manage how I sign in.
3. Select Add a new way to sign in or verify.
4. Choose one of the available methods:
   • Recovery email — use an address you can reliably access.
   • Microsoft Authenticator — verification can work even when the device is offline.
   • Passkey — signs you in using your face, fingerprint, or device PIN.
5. Complete the on-screen verification.

Microsoft specifically notes that Add a new phone number might not be available and that only these alternatives may appear.^2^

This is an account-side change, not a Windows 11 setting, so changing Windows security or privacy options will not restore the phone choice. Passkeys and verified email are Microsoft’s supported replacements for SMS; passkeys are also resistant to phishing and SIM-swap attacks.^1^

References

1. Microsoft to stop sending SMS codes for personal accounts
2. Microsoft account security info & verification codes | Microsoft Support