It's a feature: "More of the SPAM calls from Virgin, that you love...." is VM's marketing hype :)
Hey, they are giving you something for free, don't you love the value-add!
The current strategy for VM is to cold-call with offers some of the time, but they usually will try and send a red postcard thing in the post and email to get your attention by mentioning free additions to your package. The focus is on analysing customer data and who they think will be a candidate for churn (i.e. leave) based on various metrics, then they target BEFORE end of contract. Just a price reduction does not increase customer's PERCEIVED value of what they are paying for, so they are trying to do things like next broadband speed for free if you re-contract or minimal increase for customers on lowest tiers to go to a much bigger tier.
It's so you don't look away and research other provider's offerings (which can be cheaper and faster in case of Broadband). They need as much funding as possible, because at the moment, the ALTNETS are causing churn, and even BT roll out of fibre ha enticed customers to leave, despite pricing being in realm of VM's new customer or retentions offers generally. VM are praying the ALTNETS get into financial difficulty, from a business perspective, so they pounce and consolidate into VM/NexFibre. Less competition is ultimately better for them.........