Three

Terrible customer service, terrible coverage, terrible network quality, terrible online account… Just cheap

Well, I signed with my friend contract with three. It was the biggest mistake we have made. Any time you need to solve problem (and you get a lot of problems with three) you need to call them. It takes ages and very often (= almost always) person with who you talk does not know english. So it is very hard to communicate.

Your signal can disappear for few days and it is perfectly normal. Not to mention that coverage is VERY bad…

You cannot do anything through your internet account. Always you need to call them. You cannot solve anything in store too…

Basically it is cheapest network, but mostly in terms of quality. Still to expensive for user experience they provide. I'd pay as much as £5/month for unlimited text/call/internet + iPhone 5 16 GB for £100, no single penny more. In fact now, they are not that cheaper as they used to be but still as crapy… They are not worth it…