This is incorrect, the number is Microsoft MFA (multifactor authentication), when configured in Azure, (maybe more). If you are getting it multiple times, somebody is trying to logon to a system that is configured with your number, and it wants you to answer and hit pound to verify it's you. If you aren't logging in then the number is entered incorrectly, but the multiple calls means the system is working as designed. If you were to answer the call you would hear 'this is the Microsoft sign in verification process. Please press pound to complete your verification. '