In GSM terminology, telecommunication services are divided into three broad categories:

List of GSM Service:

1. Bearer services
2. Tele services
3. Supplementary Services

Bearer services are also called as Data services. These are telecommunication services providing the capability of transmission of signals between access points [the user-network interfaces (UNIs) in ISDN]. For instance, synchronous dedicated packet data access is a bearer service.

Teleservices are telecommunication servicesproviding the complete capability, including terminal equipment functions, for communication between users according to protocols established by agreement between network operators.•Supplementary Services.In addition to these services, supplementary services are defined that modify or supplement a basic telecommunication service.

Supplementary services include several forms of call forward (such as call forwarding when the mobile subscriber is unreachable by the network), caller identification, call waiting, multiparty conversations, charging information, and call barring of outgoing or incoming calls. These call-barring features can be used for example when roaming in another country, if the user wants to limit the communication fees.