Managing personal Outlook.com account settings, security, and privacy
Hey there! Nice to meet you!
Unfortunately, you will not be able to cancel the security info change since you can't receive the verification codes from your recovery phone number (your landline number). It is also not possible to bypass or expedite this process.
Your only option is to wait for the 30-day restriction period to end, after which you will regain full control of your account.
You may 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.
Also, you mentioned that you wanted to change your landline number to your mobile number. 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"
Thank you for your understanding.
Best regards,
Darhyl