Updated on 19 May 2015.
Most mobile phones are linked to a particular network such as Virgin, Vodafone, O2 or EE. This means that the phone is locked to that network and will not work with any others.
Network operators are allowed to lock your phone because they often subsidise the cost of phones when you take out a contract, so want to make this money back before you switch to another phone company.
By unlocking your phone you can use it on any network you like which means:
Unlocking your phone is entirely legal as long as you have not reported it as stolen or lost.
However, unlocking your phone means altering it, which can invalidate the warranty. If your phone is expensive, it might be worth insuring it if you unlock it; read our guide and use our comparison to find the best policy for your phone.
Start by calling your existing network and letting them know you want to unlock your phone. Each network has different rules on when you can unlock your phone, how much they will charge you and how long the process will take.
Some networks will unlock your phone for free, so check this tool on the Ofcom website to find out your network's policy. Some networks charge up to £20.
You will probably need the following information when you call:
Your provider will then give you an unlocking code. When you have this, you can put your new provider's SIM card into your phone and enter the code. It will then display a message to let you know it has worked.
If you have an iPhone and need network specific instructions, read our guide to your options
If your network charge you to unlock your phone, it is worth seeing if you can get it done cheaper elsewhere. Some phones can even be unlocked for free using a code you can find yourself on the internet.
However, it is worth noting that not every kind of handset will be covered and you may not be able to find a code for your phone.
You can find out if a free unlock code is available for your phone or get a range of quotes for a paid unlocking service using the Unlockapedia on Giffgaff's website. Compare the price of each service and how long it will take to what your network quoted you.
You can also pay a fee of around £10 to get your phone unlocked on the high street, either at an outlet dedicated to this service or at your local phone shop, but it's worth shopping around to get the best deal.
Some will do this with a code, like the online services, and you may feel that being ripped off is less likely in person. Others will handle the process manually, using a cable to attach it to a computer and some specialist software.
You can also buy the equipment to manually unlock your phone yourself online, although it is only worth considering if you are confident in your abilities in tinkering with technology!
If you are thinking of unlocking your phone it is worth making sure that the fee you pay to unlock it will be outweighed by savings you will make by having the freedom to switch networks, otherwise it may be best simply to stick with your current network. You could always try to haggle your way to a better deal!
Once you have unlocked your mobile, read our guide to help you find the best SIM-only deals.
Written by Sally at money.co.uk
The new Apple iPhones have arrived! To celebrate we've found the very best money savings apps available to download to your new device. Here's our top 10 innovative finance apps.
Being stuck without signal can be frustrating, but does it mean you can ditch your network and break your mobile contract without charge? Here is when you can cancel your contract without facing a hefty fee.
When you look for a new mobile contract, you don't always need a new phone too. Here's why a SIM-only mobile contract can be much cheaper if you don't need a new phone or want to buy one separately.
If you're looking to upgrade your phone or your contract, haggling with your mobile phone provider can help make sure you get the best deal. We look at how to give yourself the best chance of bagging a bargain.
Protect your bubble iPhone Insurance
Protect your bubble Mobile Phone Insurance (excl iPhone)
Protect your bubble iPhone 6/5/5S Insurance
Top 10 iPhone 6 personal finance apps
Can you cancel your mobile phone contract if you can't get signal?
How do SIM-only deals work?
Should you haggle with your mobile phone provider?
How Do Mobile Cashback Contracts Work?
iPhone 6 Too Expensive? Sell Your Old Phone Here to Cut The Cost
How to find a cheap mobile phone deal
How to Make Pay-As-You-Go Phones Work for You
How Much Do You Spend on Your Mobile Each Month?
6 cheapest nano SIM only deals for iPhone 6
Get expert tips that will help you spend and save smarter, even if you're short on time.