Virgin Media Calls are becoming ridiculous

Hello,

I keep getting calls from the virgin media sales team. I know they're not spam calls as I've answered them and they are Virgin Media. 

I've told them several times I'm not interested in upgrades, my communication settings is set not to receive marketing stuff and to be fair when I tell them I'm not interested. They do stop for awhile. 

However, it's getting ridiculous, I got a call at half past 4 today. I answered, then hung up because it was sales 

Then another call at quarter past 8! However when I answered, the line went dead. 

I know some people might say Just tell them you're not interested but they won't stop. I've tried just saying I'm not interested and one of the last ones said, "oh we'll call back when you have time" 

Another one, I said Unless you want to give me exactly what I've got for a cheaper price, I'm not interested in any adjustments and they proceeded to offer me a TV package. 

How do I stop this? It feel relentless as the calls come every couple of days and multiple times in that day.