A method pertaining to a telecommunications system for handling supplementary services for a mobile unit. The system includes a public land mobile network to which the mobile unit has subscribed. The mobile telephone network includes a main switch or gateway switching center to which there is connected a home location register. The mobile unit services are stored in this register. The method includes the steps of sending an authority word belonging to the mobile unit and the identification of the mobile unit to the home location register from a telephone unit in the telecommunications system via a telephone connection intended for handling services; checking the authority word by comparing the word with an authority word known to the home location register; accepting the authority word received from the telephone unit; sending a service handling specification from the telephone unit to the home location register; and performing the specified handling of the service.