Hi Nikita,
For this you will have to contact the support team, provide the details of the Azure Tenant (ID, Subscription details etc), prove that you own the custom domains in the Azure Portal that you have setup, prove with one of the mail ID and respond to the identity team via that mail ID.
Global Contact Number - https://support.microsoft.com/en-us/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
Hope this helps.
JS
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