If you want to join Three but you don't want to get a phone or tablet from us, take a look at our SIM Only offers. They're ideal if you've already got a device you love and just want a way to get connected. It's easy to get started with your Three SIM. Just slide it into your 3G handset or tablet, make sure it's unlocked for the Three network, and you're ready to go. Welcome to the UK's fastest-growing mobile network.