A service call between a service user and a call center for a service provider is established when the service user is contacted or calls into the call center of the service provider. The service provider may request basic account information for verification of the identity of the service user. If the service provider determines that a further verification of the user's identity is necessary, the service provider may send a verification code to the service user via the user communication device. The verification code is relayed back to the service provider. The transmitted verification code and the relayed verification code are compared and if the codes match, the user is authenticated.