good idea trying another network SIM in your phone so at least now you know your phone is OK. - I assume therefore that it's an unlocked handset?
Are you on p.a.y.g or contract with Virgin – is your account upto date?
With your Virgin SIM in are you able to go into the phone settings & manually select a network? - It may say T mobile or EE, not just Virgin.
if you’re still unable to connect to the network you could give Virgin mobile customer services a call on 789 from another Virgin mobile or 0345 6000 789 from any other phone and see if they can help. (It may be a problem with your SIM or it may just be an area fault that hopefully they're onto).
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