Hello there,
May be you can try the account recovery form.
The steps below will help guide you when filling out the account recovery form. It can be a lengthy process as it's designed to ask questions about your account that only you can answer. Microsoft will review your answers and respond within 24 hours.
Help with the Microsoft account recovery form https://support.microsoft.com/en-us/account-billing/help-with-the-microsoft-account-recovery-form-b19c02d1-a782-dee6-93c3-dc8113b20c42
Similar discussion here https://answers.microsoft.com/en-us/outlook_com/forum/all/how-to-verify-account-without-a-phone-number/4b98eb34-e4e1-4073-bd53-32f557b0c37f
Hope this resolves your Query !!
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