come posso aggiungere il numero di telefono

Hello, thank you for reaching out to Microsoft Q&A.

Could you please let us know where exactly you are trying to add your Phone number?

1 Do you want to set the Phone number as an Alias here?

https://go.microsoft.com/fwlink/p/?linkid=864833

(OR)

2. Trying to add it as a security Verification method so that you can receive the verification code to confirm your identity during the sign-in.

https://account.live.com/proofs/Manage

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If you are trying to add it as an alias (option 1), make sure the phone number isn’t already associated with another Microsoft account. A phone number can only be added as an alias to one Microsoft account at a time.

Also, make sure you have selected the correct country code.

If you are receiving an error, try using another phone number from a different carrier and see if it works. This may help us determine whether that particular carrier is blocked by Microsoft.