I have lost my sim whilst switching it to another phone.. I want to block it becaube I'm in Thailand and won't be returning to UK until May 2019
You need to call Virgin Mobile asap on 0044 345 454 1111 and select option 2 for mobile and select the option for lost or stolen mobiles.
If you have access to skype then dial 0044 800 183 1234 this call is free and you must select option 4 then option 1
They will block this sim and send out a new one, even if you find it the old sim will no longer work.
Welcome to the community and thanks for your post, although I'm sorry to hear about the loss of your SIM card.
What we'll need to do is make sure this is barred as quickly as possible, to avoid it being used and any charges incurred.
I'll pop you a private message, so if you respond to that with the details requested I'll be able to get this arranged.
Virgin Media Forum Team