A method comprises the steps of establishing a call between a first user equipment and a second user equipment, acquiring the identity of the second user equipment, and providing the identity of the second user equipment to the first user equipment. The invention has the advantage that it enables a law enforcement agent (for example a police officer or investigator) to track the equipment that is used by a person for a particular call. When a suspect call is received, a law enforcement agent can easily return a call to that phone, even when the SIM card of that phone is swapped. When placing a call to a suspect number, the law enforcement officer can easily determine on which device the call is answered and then determine which other persons (MSISDNs) have been using that device.