Ofcom, the organisation that's in charge of technical telephony stuff like the UK's mobile and fixed-line infrastructure, uses O2 for all of its internal staff mobile phone contracts. At a cost of around £175,000 per year.
Not that O2 is the only contract it pays for for its staff that need on-expenses outside connectivity. It connects some to Vodafone if they can't get O2, and some to EE if they can't get O2 or Vodafone, and some to T-Mobile if they can't get O2 or Vodafone or EE where they live, with deals arranged through the Crown Commercial Services Framework to ensure there's an element of bidding and competition on prices.
But O2's the clear winner, with a freedom of information request placed by Mobile revealing that the regulator has 514 O2 connections comprising of SIMs and data accounts, 13 corporate Vodafone accounts, just one person on EE and nine on T-Mobile. Ofcom explained: "The main corporate service provider for Ofcom is O2. We also use EE, Vodafone and T Mobile to ensure coverage for colleagues who are unable to obtain an O2 signal at their home location. The average annual spend (over the past three years) is around £175,000." [Mobile]