Okay, I am a VM customer of well over 20 years. My package was termed Full House with Oomph.
The package came up for renewal and I was told I could no longer include the SIM and it would need to be a separate contract, no problems there.
After a few months I started to get calls from 0800 183 6408 telling me my SIM was due for renewal and I was due an upgrade for a new phone.
I have never had a mobile from VM, only a SIM. I kept getting calls and I kept telling them to stop calling me.
I eventually used "live chat" and complained. They told me my SIM was a rolling 1 month contract and was not due for renewal and they noted I didnt want the calls to continue. I received a copy of the live chat showing this.
The calls did continue. I went back over texts and found one that said text NO to 80159 to stop receiving calls. I did that and received a reply that said "you have opted of receiving special offers...."
I thought that would be the end of it but received more calls, I decided to block the number.
Today I received a call from VM from 0800 183 6411. They told me I was due an upgrade and what new phone could they interest me in.
Log into 'My Virgin Media' and check you have opted out of marketing from VM.
Block the new sales number on your phone.
Make a formal complaint to VM first of all via VM's complaint process (unlikely to result in anything useful happening but a required step before complaining to the ICO).
Once you have the outcome of your VM complaint (and depending on whether the sales calls stop) then make a complaint to the ICO, specifically in regard to receiving unwanted live sales calls from VM and the fact that VM is ignoring your instructions to stop calling.
I have found the ICO helpful in the past on a data-protection issue I had to deal with (very slow to respond/process the matter but they achieved a useful outcome for me eventually).
As per @goslow regarding My Virgin Media, but also log into your VM mobile account
(You need to stop marketing from both the media and the mobile accounts)
Click on My Profile from the top navigation bar, then the dropdown My Preferences
This opens the marketing consent page where you can check and edit your preferences.
It takes up to 28/30 days for the changes to take effect in both accounts.