Hello,
After speaking to a CMS operator for virgin they advised me that Virgin customer numbers will be randomly switched to virgin network without any notice as it's a computer auto generated system. They will then switch over to O2 networks.
This is actually very annoying as I have no signal for Vodafone or O2.
Virgin said there is nothing they can do as they also have no access to Vodafone systems for at least 18 months.
Virgin released my PUK code free of charge with no cancellation fees due to me having no signal.
Hope this helps anyone with questions