Maybe you need to keep answering and tell them a few more times to stop calling? Seriously? Why would you expect criminals to honor your wishes? Try not answering when they call. Also get on of these:
Call Blocker
You need to buy a standalone call blocker, call blocking phone, use your carrier’s call blocker if they offer one, or download a free call blocking app for smart phones. For conventional cell phones, assign the number a letter like “z” and make no ring. You may also need to have your carrier increase the ring time to avoid having them leave a message on your voice mail.
Received a call then they hung up when I answered. I notified them I was informing both my carrier and the FCC if they contacted me again. I told them they were listed by hundreds of folks as scammers and that if they contacted me I would take action! Then I blocked them.