A service request (SRV) comprising a second identifier belonging to a collection of identifiers identified by a first identifier (WPSI-I) is rejected or allowed to proceed depending on whether the current usage data stored in relationship with the first identifier reaches a value established by usage limit data stored in relationship with said first identifier. Current usage data is updated according to service requests comprising a second identifier belonging to said collection and allowed to proceed. The usage limit data can state maximum number of simultaneous communications, or maximum number of second identifiers belonging to said collection, and can be dynamically updated according to traffic load conditions in an apparatus of the telecommunications system. The invention prevents overloading resources in telecommunications systems when the number of eventual users can not be foreseen.