If you've ever bought a handset as part of a contract or pay-as-you-go deal, you'll know that one of the minor irritants that can cause a problem further down the line is when you discover the device is locked to the original network.
This usually comes up if you want to switch to a different provider, but keep the same handset. But it can also be a problem if you're travelling abroad and want to get a local SIM card in order to avoid costly roaming charges.
So in order to avoid any anguish when you get your new SIM card – whether you've just touched down on holiday or are hoping to take advantage of a better offer from a rival provider, telecommunications regulator Ofcom has put together a new guide to make sure you can unlock your phone safely and quickly.
Who locks their phones?
Whether or not your phone will be locked to one particular network when you buy it will depend on who you bought it from and what type of deal you're on. With some exceptions, the chances are if you're choosing a pay-as-you-go (PAYG) offer, you'll have to get it unlocked before you replace the SIM with one from another provider.
EE, Vodafone and O2 all provide locked devices on these deals, while Tesco Mobile and Virgin Mobile may sell certain handsets unlocked – but this is likely to be the exception rather than the rule, so it's best to check if you're unsure.
Again, when it comes to pay monthly deals, EE, O2, Vodafone and Tesco Mobile customers are likely to end up with locked phone – though Virgin offers unlocked devices on its monthly contract deals.
The big exception here is Three, which is the only one of the UK's major network providers to have done away with locked devices altogether – something it's keen to emphasise, as you'd expect.
Danny Dixon, head of customer strategy at the firm, explained: "Unlocked phones give consumers a choice as to how to use what is on their handset. We'd rather focus on making the services we offer attractive and useful rather than limiting what our customers can do with their phones."
How do I go about unlocking my phone?
There are a whole host of mobile shops that offer unlocking services, but they're likely to charge and you have to ask if you really know what you're getting from them. Alternatively, all the providers will unlock your device if you ask them nicely – and in some cases they'll even do it for free, provided you've met certain conditions.
But every supplier has slightly different rules for when they'll unlock your phone and at what price, so this is where things get a tiny bit complicated, and Ofcom's new guidance could come in handy.
EE, for instance, won't let you unlock a phone until you've been on a contract or PAYG deal for at least six months, and it charges a fairly hefty £20.42 for the privilege, regardless of your contract type.
O2, on the other hand, let's you unlock a pay monthly device whenever you like – and it's free. But if you're on pay as you go, you'll have to have activated the device more than 12 months ago and shell out £15.
Meanwhile, over at Vodafone, it's the other way around, with it perfectly happy to unlock a PAYG phone at any time, provided you give them £19.99 of your hard-earned cash. Pay monthly customers have to wait three months into their contract before they can unlock their phone – but it's free as long as you've had the contract for over a year.
Further confusing the issue, Tesco Mobile lets you unlock a PAYG or pay-monthly device at any time – at £20 for those under a year old and free thereafter. But while O2, EE and Vodafone promise to unlock it within ten days, you might have to wait up to 28 days with Tesco.
If all this has left you scratching your head (and frankly, why wouldn't it) you can check out the exact terms and prices for your provider on Ofcom's website.
Pressure to change?
With Three now offering fully-unlocked phones and Ofcom's new guidance showing clearly the differences between the other providers, this could help pressure firms into changing their locking policies – and this is something that would be welcomed by many consumers.
A survey earlier this year by Which? found 80 per cent of people think provers should automatically unlock devices at the end of their contract, while executive director of the group Richard Lloyd described the current situation as a "minefield".
He added: "We want providers to either sell handsets unlocked or unlock them for free at the end of a contract, so people are able to switch to the best deal for them."