As well as allowing an owner the chance to consider several networks, there are a couple of other good reasons why you need to unlock your phone even before your contract ends. When you find yourself moving overseas for instance, you might want to take advantage of a local SIM-card while you are there to stay away from expensive roaming charges. Or maybe you've decided to sell your mobile phone then you'll probably get more money and a lot more interest in a smartphone which is free to work with with every network carrier.
You'll find nothing illegal about unlocking your mobile. It is your phone and you're within your legal rights to use it on any network you choose. Still, there's a chance carrier unlocking your cellphone will void your warranty, so it may perhaps be best to hold-off until you have completed your contract before you make a decision to leave your existing network.
You should make sure your cell phone actually needs SIM unlocking by entering a Sim from a different network provider into your mobile device. If it's locked, a message will pop-up on your phones home screensaying it's locked. The quickest way to SIM unlock your device is to call your provider and ask for a Network Unlock Code (NUC). Just about all will give you one and some even do it without charge once you've finished your contract. When you're given your code you ought to be capable of enter it into your smartphone to remove the lock. This is the easiest and most reliable method of IMEI unlocking.
As soon as your cellphone is unlocked, you will be ready to find one of the cheapest mobile packages out there - a Pay-As-You-Go package. All these usually operate on a rolling month-to-month basis, which means you can utilize the package for so long as you are happy with your device and then up-date when a shiny new model is dropped or your old device sooner or later fails.
If you are not sure which website you can trust, I highly recommend Unlock.Zone. They provide unlocks for all major manufacturers and carriers, provide a guaranteed price match promise, but first and foremost, have a 100% refund policy in the unlikely event they can't unlock your phone. I have used them personally and was really happy with the service I received and ultimately that they successfully unlocked my cell phone.
Here's a link to their home page: IMEI Cell Phone Unlocking Service