Useless set of SCAMMERS who pretend to be O2 and wanting to send me a new sim card. Usual process, first one person tries to catch you, then they pass you to a supervisor, who sends you a code to access their system. If you go on beyond this point you are open to serious financial issues, so DON'T just HANG UP if you haven't do so already. Plus do not ring the number they give you.