O2 (UK) O2 (UK) Telefónica UK Limited (trading as O2 – stylised as O) is a telecommunications services provider in the United Kingdom, owned by the Spanish multinational Telefónica, and is headquartered in Slough. With 25 million subscribers (as of December 2017), O2 is the second-largest mobile network operator in the United Kingdom after EE, with Vodafone in third place. O2 was formed in 1985 as Cellnet, a 60:40 joint venture between BT Group and Securicor. In 1999, BT Group acquired Securicor's share of Cellnet and the company was later rebranded as BT Cellnet. In June 2000, BT Cellnet launched the world's
O2 Czech Republic O2 Czech Republic O2 Czech Republic (operating under the O brand) is a major integrated operator in the Czech Republic. It is now operating more than six million lines, both fixed and mobile, making it one of the Czech Republic’s leading providers of fully converged services. O2 Czech Republic operates a fixed and mobile network including a 3rd generation network, CDMA (for data), UMTS and EDGE, enabling voice, data and video transmission. O2 Czech Republic is also a provider of ICT services Previously two companies, fixed-line operator Český Telecom and mobile operator Eurotel, it was acquired by the Spanish company