How do I convince my Dad to stop giving money to scammers?

I don’t know all of the details, but basically my dad is convinced these scammers are a crypto company. He’s poured a lot of money into them, and they’ve told him he has around 1 mil in crypto. I don’t know anything about this stuff, just what he’s told me, but what makes me believe they are scammers is the fact they won’t give him any of his “money” or show any evidence he actually has it. They keep asking him to give them more money as a “payment” for the 1 mil they’ve helped him get. My dad who was at first skeptical, is continuously giving them money without me knowing, because he knows how much I hate that he’s doing this. I genuinely have no idea why he’s still communicating with them, I think he’s obsessed with the idea that he may actually have the money. But either way no matter what I say he still talks to them and is still currently giving them money. I don’t know anything about these scammers otherwise. I genuinely don’t know what to do to convince my dad to stop.

Edit: For further context, I’m 16 yrs old, so there’s not much I can actively do to prevent my dad from talking to them, I probably should’ve specified earlier, but I’m looking for any advice or suggestions as to how I can prove that he is being scammed/how to talk him out of it. The weirdest part about this is that my dad was at first concerned that they were scammers, and actually talked to a guy who specializes in this kind of stuff at our city police station, but has now completely backpedaled and is communicating with them again. I’ve told him to stop numerous times, but he either tells me he “has it under control” or just ignores me and continues to contact them privately. So, any suggestions or info on how to help my dad?