A method and system for updating a table of correspondence between a logical address associated to a user unit in a communication network and a unique identification number associated to one of a group of user units managed by a management center, a method where messages are exchanged between said management center and a specific user unit of said group by using said communication network, these messages being forwarded to the logical address of the specific user in said network, the method including searching in said table for the logical address of the user unit in said communication network corresponding to the unique identification number of the specific user unit; sending of messages to the user unit having the concerned unique identification number, to the logical address corresponding to said communication network; and if the messages are received incorrectly, sending a request containing an identifier of said specific user unit.