1. A method for collecting user activity information in a telecommunications system comprising a routing node handling signaling messages of the terminal of a user and a location registration node handling registration information of said user, comprising the steps of: a) sending from the routing node to the location registration node a message notifying a registration event of the user, where the message registers, re-registers, or de-registers a presence of the user via the terminal in the telecommunications system, and b) updating, by the location registration node, registration information of said user according to the content of said message; wherein step a) further comprises: a1) sending in said message an information element indicating whether said user has been involved in a service provided during a registration period comprised between a previous registration event of said user and the registration event notified in the step a), and step b) further comprises the step of: b1) updating, by the location registration node, activity information of said user according to said information element.