If you combine VM services with an O2 SIM you become eligible for some further package benefits which VM calls 'Volt'.
https://www.virginmedia.com/virgin-media-o2
Whether or not these benefits are really that useful, and VFM, might depend very much on the individual circumstances of each customer.
VM's sales model has always worked on the idea of providing 'bundles' of services in return for discounts on the services in the bundle.
VM O2 presents itself as a single organisation but, in practical terms, you end up having to deal separately with O2 for the mobile side of the deal and VM for the other services.
If you are receiving unwanted marketing calls from VM, first thing to do is to opt out of marketing in 'My Virgin Media' if you have not done so already. Next start blocking the numbers as the calls come in (VM may call you on many different numbers).
The only way to get a good deal at renewal is to get in contact with a sales agent and haggle for what you want. VM's sales agents will always try to upsell you to the biggest/most expensive package they can push onto you. Best defence against this is to do your research in advance and have prices from local competitors at hand for the services you want and use those as your benchmark when comparing any offers from VM.
