I stick with O2 because I get a signal in my rural locality and I find the signal is good nationwide even when I'm with people who are complaining they have no signal and they turn out to be on EE or Vodafone. The big big big problem is their appalling customer service and their ability to make a complete mess of anything you ask them to sort. Two years ago it took me several hours to sort a mess after change of contract. Now, I am trying to resort the contract, the chatline made a complete mess of it yesterday and today I have spent the whole morning on a chat and they will not ring me or answer the phone to sort it - they just keep messing up the chat - I think they are doing it on purpose to try to charge me £27 rather than let me use the £15 sim bundle I am trying to swap my number onto. I'm now gonna sit and have a chat with Siri, Cortana or Bixby so I can feel like I'm having a chat with an intelligent being after O2's chat team have totally messed with my head