virgin mobile knew if the problem when I moved house in January. After new simcards were tried we decided that the signal wasnt going to work and that the account is closed as I changed to Tesco mobile in March. I dont remember seeing a letter to confirm this but there should be recorded phone calls??
If they were still polling the DD, sounds like the account was NOT closed. Might be worth starting there. Your issue is if you have no correspondence confirming the account was closed, its likely going to be difficult to get a refund.