O2 (UK) Telefónica O2 had a long-standing relationship with Arsenal F.C., being their shirt sponsor until the end of the 2005/2006 season. In 2005, a three-year deal was signed that saw Telefónica O2 become the team's exclusive mobile communications partner. O2 were the main sponsor of the Channel 4 reality TV show "Big Brother" from its second series (as BT Cellnet) in 2001 until its fourth series in 2003. They also sponsored the spin-off shows "Celebrity Big Brother 2" in 2002 and "" in 2003. In total O2 sponsored five series of the show. O2 sponsored music festivals, the Wireless Festivals, from
O2 (Ireland) available to customers paying similar amounts in the UK. Less than 48 hours after the much hyped launch of Apple's latest model, owners of all phones on the O2 network discovered they could not access the internet at all due to a network failure. Further criticism came from iPhone customers regarding the continued failure of O2 to deploy Visual Voicemail. O2 was the only carrier in the world to launch the original iPhone without Visual Voicemail, one of its headline features. O2 was responsible for the highest number of registered judgments, which financially blacklists those people who do not pay