If you've bought a Samsung Galaxy S3 from a network and want to use a couple of different SIM cards in it -- maybe you're on Vodafone but want to use Orange Wednesdays -- here's an easy way to unlock it.
The simplest way is to get something called a network unlock code from the phone's original operator, which will open the barriers and let you use any SIM you want. Annoyingly, some networks aren't always keen to provide this number, leaving you to search for other alternatives.
A quick Google search shows there are a bunch of websites that offer to sell you these unlock codes for varying amounts of money, but I wouldn't recommend parting with a single penny without asking around on phone forums whether anyone else has had any success.
Alternatively, you can grab a simple app from the Google Play store called Voodoo Galaxy SIII SIM Unlock which -- as the name suggests -- unlocks the handset. The only problem with that is you'll need to have your phone rooted, which basically means stripping out all security features letting you have full control over all software on the device.
It's a potentially risky business and will certainly void your warranty, but many droid users love using custom software and special apps that are only available on rooted phones. Rooting the S3 isn't a difficult process and I've put together a full guide on how to do it over here. I'll say again that CNET takes no responsibility for any damage to your phone as a result of following these steps.
In brief, you need to download a program called Odin 3 and the rooting software called CF-Root-SGS3-v6.4. Connect your phone to a PC, back it up and install the latest drivers using Samsung's Kies software then disconnect it. Extract and install Odin and then extract the CF-Root file, giving you a .TAR file.
Load Odin, click the button marked 'PDA' and load in the CF-Root file. Turn your phone off and then press and hold volume down, the power button and the home button until it boots and then press volume up to set your phone to download mode. Connect it back up to your computer and click start in Odin. If all goes well then your phone should now be rooted and you can run the unlock app, removing all the network bars in place.
This then allows you to pop in any SIM card you want. So if you've bought an S3 second hand that's locked to Orange, but you want to use your existing O2 tariff with access to the Priority Moments deals, that should now be fine.
Have you tried rooting phones before? Are you keen to unlock an S3 to use with your existing SIM? Let me know in the comments below or over on our Facebook page.