I can see from what little info I found from Virgin and the web, NETWORK KEY is being misunderstood as Unblock code, Unlock code, Sim code etc. and it seems to be a long-standing problem.
3 identical phones, 2 phones are now ok, thanks to a call to 789, being given a NETWORK KEY and then a SERV PROV code, but third phone has had two keys which didn't work and now says LAST TRY!. I don't know if that means there one more try or that's it.
Customer Services need to be told how to deal with this. I kept being asked where I'd bought the phones without being given an explanation.
From a previous post and what I've found on the web, it looks like my 'Virgin' phones are possibly 'locked' to EE network. A solution seems to be to get an ASDA EE Sim card and leave Virgin and presumably lose credit, if the phone is not now permanently locked.
Far from being a 'FREE' Sim, I've already wasted £6 on calls and texts, Virgin and my time being wasted and I could be further out of pocket for a new phone. If so, will Virgin compensate?