network lock

[WillGibbins]

hi guys, so i have a motorola razr v3 that i bought from CEX a few years ago. It works with my o2 pay as you go sim and a pay as you go giffgaff sim and it used to work with my ee sim but when i try with my current three sim only sim it says check sim which i assume means there is a network lock but im not sure to which network and how to unlock it. what can i do? thanks

[MI5 · Accepted solution]

@WillGibbins 

How to unlock an O2 phone here Guide: Unlocking an O2 phone to use a different SIM card 

[WillGibbins]

yeah i tried following that and no luck, i even contacted o2 but they said my phone wasnt locked to o2? even though thats the sim it works with

[MI5]

If the EE SIM works too it won't be locked so check the three SIM is working ok and fitted correctly.