'network rejection cause mm #6' issue.

[Simon22]

Hello!
I am hoping someone may be able to help me please,

Background: I bought a new phone back in June because my old one had a crack in the screen which was only going to get worse. It is a Sony Xperia L3, SIMfree, and the wireless carrier is O2, the same as my current SIM. I swapped over the SIM to test and as far as I remember everything worked fine. 
I had some issues with 'Hey Google' setup which I didn't want but there wasn't any get around. I switched the SIM back to my old phone because of the details and app etc. on it which I needed for work that day and tried to get my use out of my old phone.
I've gone to put the SIM back into my new phone for permanent use now, and I get this error message, even after a factory reset (Sorted the 'hey Google' out this time). I can get onto the internet and Whatsapp works fine, but I cannot make and calls or texts:
network rejection cause, phone not allowed MM #6 
(O2 - UK (data connection only.)

So far I've tried turning airplane mode off and on, and selecting the networks manually.
I've tried sending of both IMEI numbers (dual SIM) to O2 for unlocking, but both have come back with a:
'I'm sorry, we have not been able to unlatch your device at this time.
The reason given is:
We were not able to find the details in our system, the handset is not
an O2 device

It should be an O2 phone, I cant find anything on settings telling me otherwise, I don't have a SIM for another network to test either sorry. Any advice or help would be appreciated please 🙏

[pgn]

Seems you may have a phone that is locked to a different carrier, @Simon22 - https://joyofandroid.com/how-to-remove-phone-not-allowed-mm6-error/

[Simon22]

Ah thank you, so it is on the wrong network. How do I find out which network carrier it's tethered too please, there is nothing I could see in 'about phone' or other settings. I did a quick google and there are sites but they all look super dodgy and want money.

[pgn]

Awkward as you bought the replacement back in June, I think, @Simon22 - I have not used this website, so tread carefully: https://www.techbout.com/find-android-phone-unlocked-locked-22897/

[Simon22]

When looking through it seems to have wanted to give me my SIM network details as it does it by phone number, which I already have. Though it appears I may have a bigger problem, two different IMEI checkers gave me details for GFIVE mobiles when I popped in my IMEI, I thought it was some tech company that had worked on some part of the phones internal workings but began to suspect it might be the mobile network carrier. After googling to be sure, I realised it's a phone manufacturer like Sony, so my IMEI is linked to a different phone? Is that even possible?

[MI5 · Accepted solution]

@Simon22 

Where did you get the phone from?

The only way it can have a G'Five allocated IMEI is if the phoned was barred and someone has cloned it.

Obviously this is fraud and the phone likely was stolen or the subject of an insurance claim.

The system has now picked up on the cloned IMMEI and barred that too, so effectively, the phone is useless.

[Simon22]

I got it from Amazon, STARSMARTSWORLD is the seller according to the email. The reviews were pretty positive (4.5/5 stars, some 500 ratings) the 1 star reviews were mostly people who bought used as opposed to new and got phones with cracks etc. so I figured that didn't apply to me as I bought new. Looking at ****** now it seems it's just general product reviews, with Sony Tech team answers as opposed to reviews of the seller? I can't find that particular seller listed in the options anymore, but I might just be dim.

My phone is def a Sony Xperia, but if the IMEI sites are listing the GFIVE as the default for the IMEI then mine is the dud/cloned/stolen of the two I guess?
It comes back as clean etc. on the IMEI sites, but obviously that result is the GFIVE result as they think that's the phone. This has been a fun costly lesson experience, thanks for the help anyhow 👍