Deutsche Telekom AG / Zentrale des Konzerns
Telekom Deutschland GmbH

OTE (Hellenic Telecommunications Organization S.A.)
Cosmote (Cosmote Mobile Telecommunications S.A.)
T-Systems Information and Communication Technology E.P.E.

T-Systems Limited
Deutsche Telekom (UK) Ltd

T-Mobile Netherlands B.V.
T-Systems Nederland B.V.

T-Mobile Austria GmbH
Software Daten Service Gesellschaft m.b.H.
T-Systems Austria GesmbH

T-Mobile Polska S.A.
T-Systems Polska Sp.z o.o.

Combridge S.R.L.
CosmOTE Romania
Telekom Romania Communications S.A.
T-Systems ICT Romania S.R.L.
GTS Telecom Srl

Slovak Telekom, a.s.
T-Systems Slovakia s.r.o.

Magyar Telekom Nyrt.
IT Services Hungary Szolgáltató Kft.

T-Mobile USA, Inc.
T-Systems North America, Inc.