Hello,
My name is Jackson and thank you for your question.
If you have access to the old security info, you do not need wait the 30days pending period as you are just suppose to verify and update the new info with the steps;
- Sign in to your Advanced security options page using your Microsoft Account; https://account.live.com/proofs/manage/additional
- Select Add a new way to sign in or verify then choose how you would like to receive security codes.
- We'll send a security code to confirm. Enter that code when prompted and then select Next.
- That's it. Next time you need a sign-in verification code, you will see the new option listed.
Yes the message is legit and by following the option it take you to verify and replace the info immediately. see more details in the link;
https://support.microsoft.com/account-billing/cbd0f64f-02d9-45d2-90c3-2375e5a72e52
Warm regards,
Jackson E
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