Buying a second-hand phone is a great way to bring down the cost of purchasing a new handset, but in doing so, budding users can often find their handsets aren't compatible with their preferred network. To enjoy using a SIM card from another network, the phone needs unlocking. Unfortunately, unlocking a phone isn't the easiest of tasks, but to help make it a bit more straightforward, here's everything you need to know.

In this phone guide blog, we take a look at over 10 ways to unlock a phone before you sell it, explaining why need to unlock a phone and how it makes selling your device easier.

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What does "unlocked" mean when selling a phone?

When you unlock your phone, you can use any network's SIM card so you can freely switch providers, lower your costs and pass your phone on to others. It also makes it a lot easier for traders like Envirofone to get access to your phone and sell it.

How difficult is it to unlock a phone?

First up, if you're unsure whether a phone is locked, the easiest way to find out is to insert SIM cards from two different carriers in the phone, one after the other (just in case one of the cards matches the provider the phone's locked to).

If both show the network on the handset and allow you to send messages, the phone is unlocked. If it's locked, the phone will usually ask you for a 'SIM Network Unlock PIN' (different to your usual login PIN) or simply won't show the network on the top info bar of the phone. Unlocking a locked phone is 100% legal, although the process isn't always free. You can either pay the provider it's locked to a fee to unlock it, take it to an independent phone shop, or do it yourself using a code.

Can you unlock a phone from a carrier?

• Virgin Media - All monthly contract customers with Virgin are provided with an unlocked phone – pay-as-you-go (PAYG) phones aren't, however. To unlock one of these, you'll be charged £15.32 and will have to wait up to 30 days for the phone to be unlocked entirely.
• Three - If you need to unlock three phones, phones bought through Three after December 13th 2013 are all unlocked. If you bought one before this time, you'll have to phone them and ask for a free unlocking – this will take up to seven days.
• EE - Interested in finding out how to unlock an EE phone? Both monthly and PAYG phones are locked on EE. To unlock them, you have to call 150 and pay an £8.99 fee, and must have paid your contract for six months or more. PAYG phones have no time limit. The phone should be unlocked in ten days, or seven days if you've got an iPhone or iPad.
• O2 - Most pay monthly and PAYG phones bought through O2 are locked. PAYG customers must pay a £15 charge to get theirs unlocked (after 12 months of use), and the phone will be sent a code within three days of the phone unlock application form being received by O2. Monthly contract users can unlock theirs for free at any point – you'll have to see out the end of your contract, though. The phones should be unlocked within 72 hours.
• Vodafone - PAYG and pay monthly phones bought from Vodafone after July 2013 will be locked. Unlocking is free and will take ten days, but PAYG customers must have used their handset for at least 30 days.
• Tesco Mobile - Need to know how to unlock a Tesco phone? Tesco Mobile does lock both its PAYG and pay monthly handsets, however unlocking them isn’t too much of a challenge and for paying monthly customers there’s no cost. If you’ve got a newer handset however it could be a bit trickier, as there are time limits on when some handsets can be unlocked.

There is a £10 charge to unlock a Tesco Mobile PAYG phone within 12 months of being activated, but if the phone was activated over a year ago then it’s free. The phone should be unlocked in seven working days, but this varies depending on the phone and the wait can be up to 20 days.

Can I unlock my phone myself for free?

If you decide not to go with your provider, you can either go to a local phone shop or find an unlock code for the phone online. The former is usually a perfectly fine way of unlocking a phone – just check online reviews to make sure you're not caught out by cowboys and get a quote from several shops to get the best deal.

Getting a code is a little different. Although lots of unlock code providers are legitimate, you could end up paying more than you would if you went to the phone's provider. There are also lots of sites offering “free unlock phone codes”, but you can sometimes be provided with a completely useless code, so do your research. Unlocking a phone is a lot easier than it used to be, and providers are slowly becoming more open to the idea of unlocking. Just be sure to watch out for less reputable services.

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Conclusion:

Still unsure? Our FAQ section is great for answering any more of your queries, or feel free to email us with your troubles so we can help sort out your phone! We have plenty of cheap phones unlocked on our website too including Apple, Samsung Galaxy and more, so make sure to check them out.