The present invention relates to a method for accounting a particular user accessing a prepaid service, which prepaid service being supplied by a service provider, which communication device being coupled to the service provider via an access control unit, and comprising the steps of: sending an authorization from an authentication server to the access control unit to authorize the particular user to access the prepaid service, thereupon, granting the communication device an access to the prepaid service. A method according to the invention further comprises the steps of: sending a notification from the access control unit to an accounting server to notify that the particular user gained access to the service provider, decrementing a quota allotted to the particular user according to a service usage, after the quota is exhausted, sending a request from the accounting server to the access control unit to disconnect the particular user from the service provider, thereupon, locking the access to the service provider. The present invention also relates to an access control unit.