Absolutely dreadful mobile network provider! I strongly advise not to join or use O2, as their mobile provider. They message me stating that they no longer provide service to any old simcards. But the funny thing is these 'Old Simcards' come with 'Long-Term Customers'. But this is obviously something a gluttonous business, such as O2, don't really care about! They even send out automated messages, after requesting your PAC code. Stating your Sim Serial number, existing credit (if you are Pay As You Go). In addition to the telephone number to contact, if you wish to get a refund. Good luck trying to get your refund though! The automated message specifically states to call, "...after completing your switch". However the O2 Department say that they require you to, "Still be an existing customer and have an O2 account, to receive any possible refund". The whole business is run extremely poorly. Whilst I am glad that I have left such a dire Network provider, I do still feel scammed. O2 has basically kept all of my unused credit and were unable to provide the refund; which they themselves stated in their message, in the first place! 1/10