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 then remove your outdated recovery phone number by clicking the option "Remove"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, Microsoft has recently phased out the option to add a phone number to a Microsoft account, as stated in this article, particularly under "Notes": https://support.microsoft.com/accounts-billing/manage/microsoft-account-security-info-verification-codes
However, you can add other verification methods, such as a recovery email address, a passkey, and Microsoft Authenticator on account.microsoft.com > Security > Manage how I Sign in > Then click on "Add another way to sign in to your account"
Please let me know if you need anything else.
Best regards,
Darhyl