Measures for modifying settings of communication services for Session Initiation Protocol (SIP) devices in a telecommunications network are provided. A code-containing SIP message comprising a code entered by a user of a SIP device is received from the SIP device. The code identifies a communication service. The communication service that the code relates to is determined on the basis of the received code. A function-activating SIP message comprising data specifying one or more characteristics of at least one function to be activated by the SIP device in a data collection operation is transmitted to the SIP device. A completed data-containing SIP message comprising communication service data entered by the user of the SIP device is received from the SIP device. The communication service data is processed in accordance with the identified communication service.