The usual reason for the account being unavailable is when the VM security team lock it to protect the account holder.
You should change the account password if you haven't already done so.
Sign in to My Virgin Media, go to My Profile and/or Manage Accounts depending on whether the account concerned is your primary account or an additional one. Select the account concerned and then click on Change to the right of password if a primary account or View/Change then change to the right of password for secondary accounts.
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