Indicating a user equipment that it must register

The invention proposes a method for controlling a network, wherein the networks offers services to registered users, the method comprising the steps of receiving (A1) a service request from network device (UE) of a user, checking whether the user is registered or not, and if the user is not registered, generating a response message including a warn information and sending (A2; B3 to B4) the response message to the network device (UE) of the user. The invention also proposes a corresponding network device. In this way, a user is informed that he has to register before he can obtain any services from the network.