Managing personal Outlook.com account settings, security, and privacy
Hey there! Nice to meet you!
You can update your security info on account.microsoft.com > click "Security" > "Manage how I sign in" > select "Add another way to sign in to your account" to add your updated verification method first > then remove your outdated recovery phone number by clicking the option "Remove"
You may be asked to wait 30 days in order to update your security info. During this time, you will not be able to sign in to sites or services with your account.
Please check this link for more information regarding security info change: https://support.microsoft.com/accounts-billing/manage/what-does-security-info-change-is-still-pending-mean#:~:text=You%20were%20the%20person%20who%20removed%20the%20security,these%20security%20proofs%20to%20complete%20the%20cancel%20request.
Lastly, it is no longer possible to add a phone number as a verification method, as Microsoft has stated that they have already phased this option out, particularly under "Note" https://support.microsoft.com/accounts-billing/manage/microsoft-account-security-info-verification-codes
Thank you for your understanding.
Best regards,
Darhyl