[Update: OnePlus 3 is now discontinued from the manufacturer OnePlus. Upgraded version is now called OnePlus 3T and O2 UK exclusively carrying it.]
O2 UK, the best network for coverage, uSwitch 2016 winner selling SIM-free (unlocked) OnePlus 3 smartphones. O2 is the only network selling them in the UK. The price just starts from £28 per month without any upfront cost. OnePlus 3 is a high-end phone at an affordable price range, competing with other 5.5″ (inch) display phones. Running on for Oxygen OS 3.2.4 which is based on Android 6.0.1 (Marshmallow).