iPhone, iPad, Samsung Screen Repair Leatherhead, Bookham, Cobham, Ashtead, Dorking, Epsom, Esher, Guildford and surrounding areas in Surrey

Most devices are what's called 'locked' to the network.
This means the device will usually only work on that particular providers network. So for example, you've had a phone on contract with Vodafone then after your contract has ended, you buy a SIM-only deal with say O2, but the O2 SIM will not work in your device as Vodafone have locked it to their network.

You may also need to get your handset unlocked if you want to use a local SIM card in your handset when travelling abroad to avoid roaming charges.

There are really only four (4) mobile networks in the UK and it is usually one of these providers that you need to contact to get your phone unlocked.
These providers are: O2, Vodafone, EE, Three
(Remember, T-Mobile and Orange now fit under the EE banner)

Provider Charges Unlock Details
EE PAYG - No Charge
Contract - £8.99 or Free after contract period
Non-Customer - £8.99
Unlock your phone
O2 PAYG - £15 (after 12 months)
Contract - Free
Unlock your phone
Three Usually sold Unlocked (after 1st Jan 2014), but if locked it's free to unlock Unlock your phone
Vodafone PAYG - Free (after 30 days)
Contract - Free (after 3 months)
Unlock your phone

You can see more information on this topic from the regulator OFCOM.

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