Unsolicited Dick Videos: Asking Me For Photos

So to make this short, I’ve been recieving many texts about dick pics, and the same picture over and over of someone I didn’t know. I kept blocking the #s but it kept coming through over and over on different numbers. So I decided to ask who it was. So they told me it was “Z” for short who was a past co worker of mine. The video that was sent repeatedly was one with a blurred face and you guessed it. So I put two and two together thinking maybe he got his phone stolen or compromised and now someone is going through his contacts? I blocked them and kind of threatened them a few months ago and I ended up blocking them since it was getting pretty frequent and multiple texts. So now just tonight, I get it once again but they are trying to purchase pictures of me for $250. & I’m obviously just going a long with it to maybe see if I can get any info, but I just told them to send me the money for free ???? but insisting that they don’t wanna be scammed. They then get angry w me and started calling me names and threatening me about they’d kill me and shit. It’s kinda scary but also I know it’s just someone who may have gotten a hold of personal photos of my co worker. I really do want to look into what I can do about this. I was close to calling the cops for harassment as much as they texted and send explicit photos. What should I do? I really don’t wanna change my #.