I've had the worst experience of my entire 22 odd years of mobile phone contracts coming back to o2.
Managed to mess up a number port. Blame it on a faulty SIM despite the SIM previously working fine with the new number. OK I'll give them the benefit of the doubt.
Insist the only option is a SIM swap.
Refuse to expedite shipping for a new SIM.
Refuse to swap to a SIM obtained in an o2 store.
Refuse to escalate.
3 have a reputation for customer service which o2 are doing a fine job living up to. Whatever company they use for theit web chat customer service isn't fit to run a government department never mind an actual company that needs to keep customers.
I've been uncontactable via my phone number of years for 3 days now. My only hope if I want my number back before the middle of next week is to visit an o2 store, again, at my inconvenience and expense, and bring the id they require, but didn't tell me beforehand they require, this time.
I might not have needed that id if the My O2 section of the website had my current account details, instead of my old disconnected account. That's another thing "customer service" were supposed to fix several days ago. I can't do anything about it myself as my SIM is not connected to the network. It makes it difficult to receive texts.
In short, o2 are done. It's been downhill since Telefonica were involved and I will be telling everyone and anyone to simply avoid.
