Abstract: In a telecommunications network having a radio access network (RAN) portion and a core network (CN) portion, data records are built from messages monitored in the RAN portion, each data record including at least two different predetermined types of field values, such as time, location area, cause indicative of a cause of termination of a transaction within a call for which the data record is built, subscriber identity and at least one type of service. The data records are then enriched by providing further information into the data records including at least an identifier for each predetermined type of field value in the data records.