So after 20 years of being an O2 customer I finally switched to a new network last week. However, unbeknown to me, my handset is locked to O2. I rang customer services and spoke to the rudest customer "advisor" I have spoken to in a long time. I was informed that in no way can o2 unlock my phone because I purchased it from CEX and not from o2. The woman told me the only way it could be unlocked is if I go back to CEX and they unlock it! I mean, how? It's locked to o2, it's one of their phones, it requires their code.
Fact is, they can unlock it. They just won't. Despite saying quite clearly on their website that they will unlock any o2 phone for free (with NO exceptions). After 20 years with the same network I would expect a little more cooperation. I am stuck with a phone I cant use and a number I can't access. I have been literally off-grid for nearly a week, not able to receive calls or texts. I can't afford a new handset and see no reason why I should purchase one when I have a perfectly good one that O2 are refusing to allow me to use!
So first off check it isn't blocked on any network via the checkmend service as CEX are known for selling stolen and insurance reported phones .
If it is not listed then follow the above https://www.o2.co.uk/help/device-and-sim-support/unlocking-an-o2-mobile-to-use-on-a-different-networ...
Do not tell the CS advisor it came from CEX, just advise them its one of your old phones.