I applied and got accepted for a mobile last January never received it so assumed it had just been rejected but when I checked my credit report I have a high telecoms default on their for over £500. Surely Virgin Mobile can see that whatever sim was sent it has never been used or activated?!!!
Sorry to hear about your situation. From experience, I suspect you might have BIG problems ahead. Get ready for Virgin to assert that you MUST have activated the phone because their systems are perfect. You will spend a lot of time on the phone to customer services, who are very nice people, but ineffectual in such circumstances. Expect them to set a debt collection agency on you even though they have no proof of you using the phone.
My advice is to start writing letters rather than phoning and be prepared to seek legal assistance as soon as they assign a debt collection agency. If you are told by customer services that it is Virgin's mistake, write to Virgin and insist that they put this in writing - if you don't, this may blow up again out of nowhere (from experience, even several years later).
Customer Services seem to be less busy during the day, but if you do get through, I wouldn't take what they say on the phone as being gospel. We were told they would sort everything out, then a week later, we received a threatening letter from a debt collection agency.
Well if it has been used, they can get the police involved, whose investigations should start with ringing the most-called number to establish the identity of the person calling it.
The problem comes with whether Virgin staff can be bothered to report it and give that information. They may just ignore the problem and expect the debt collection agency to sort everything out.
Did you source a handset/contract from somewhere else? Is it a smartphone? If so, install some call recording software on the phone, phone a friend to make sure it's recording OK, then phone Virgin again to try and sort the problem out. You don't need to advise them that you are recording the call. If there is a dismissive response such as the employee hanging up, contact one of the forum staff on here, explain what happened and mention that you've recorded the call. You'll be surprised how quickly things will move from that point.