This may help, found on asda mobile q&a's....
Is my Asda Mobile phone locked or unlocked?
If you purchased mobile phone from Asda Mobile after October 2012 your phone will already be unlocked and ready to use on the new network. If you purchased your phone before October 2012 your Asda Mobile phone may be locked to the current service and you will need to unlock to use on the new Asda Mobile on EE network. First, insert your new Asda Mobile on EE SIM card into your existing mobile phone and switch it on. If 'Asda Mobile' appears on the handset screen your device is unlocked and ready to use. If an error message appears your phone is locked and if you want to continue using your existing device you will need to unlock it;
If you purchased your phone from any other retailer or mobile network other than Asda Mobile you will need to contact them to ask to unlock your phone - the network may charge you for this. Or, if you would like a new phone click here to browse our range of phones.
If you purchased your phone from Asda Mobile and your phone is locked, please click this link and follow the instructions provided where we'll provide you with the required information to unlock your device to use.
If you have followed Step 2 and we cannot locate your phone and provide you with the unlocking assistance please contact us and provide the make and model of your phone you are trying to unlock.
If you bought your handset from Asda Mobile before October 2012 your phone could be locked. If you want to join the new Asda Mobile service on EE, click here and follow the instructions provided. If we cannot unlock your phone for you, please contact us on and we will be happy to help.