O2 Sim in a new phone

[MM2]

HI

I've transferred my o2 Sim into my new phone but the network is now showing as Giffgaff.  Any idea what is happening?

[MI5]

@MM2 

Check your apn is set to O2.

[MM2]

Network selection list is offering O2 as a choice but I had a strong O2 signal on the old phone in this location.

[MM2]

Sorry - is not offering O2 as a choice.

[MI5]

@MM2 

You are on automatic network selection?

[MM2]

Automatic selection shows Giffgaff.  The phone is working normally making and accepting calls etc.  If I try manual selction of network O2 is on the list of available networks found.  Contract is with O2.

I really appreciate your help.

[MM2]

Sorry again  is not on the list

[MI5]

That's really weird @MM2 

Daft question, but you have got your O2 SIM in?

[MM2]

Yes. It came out of my old O2 phone. I've just double checked and it's definitely O2. But the phone reports having a Giffgaff SIM in

[MI5]

@MM2 

I can only guess that you don't have the O2 carrier file installed on your phone for some reason.

Is it an iPhone?

Settings >general >about. And see if you get promoted for the O2 carrier. 

If not, try connecting to iTunes on your pc.