A telephony provider is an external service that sends authentication codes or verification calls over mobile and telephone networks. In an identity system such as Microsoft Entra ID, an organization may use a supported provider to deliver SMS or voice authentication when that option is available.
Phone-based codes can provide a second sign-in factor, but they are more vulnerable to attacks such as phishing, number porting, and interception than phishing-resistant methods like passkeys. Administrators should confirm provider support, review who depends on phone authentication, and prepare and test alternative sign-in and recovery methods. Relying on an external provider does not remove the need to manage these risks.