An improved technique involves employing knowledge based authentication (KBA) to validate a user trying to reissue a SIM card. Along these lines, when a user goes to a mobile device vendor and requests a reissue of a SIM card, the vendor relays that request to an authentication server which in turn sends KBA questions to the user. The KBA questions are based on data available to the mobile carrier to which the genuine subscriber subscribes. Such data concerns information including calls made and received, amount of minutes and data used in a month, and amount billed in particular months. The vendor honors or denies the request to reissue the SIM card based on the answers submitted by the user to the authentication server.