Ken is a telemarketer and Ken's phone number is 1-417-800-2511--and for a fee he will provide a service and once Ken collects his compensation over the phone he will enroll you in his research study program, called "I'm not a telemarketer. Now give me your money and a lot of personal information so I can rip you off."

I have pressed 2 to stop calling me but they keep calling

The fact that you're on the Do Not Call list does NOT matter to scam callers. Legitimate companies subscribe & abide by the list, however, scammers do not.
Although the government can be blamed for a lot of things, this is not one of them. Many of these scam calls originate from overseas, and the numbers that display on your called id are spoofed/faked through software, and not from anywhere near the location of the number displayed. Also, pressing any option to remove your name from their calling list only makes it worse. It basically tells their system that your number is valid, and they'll only keep calling, or you'll receive calls from completely different numbers. It's similar to when you open a Spam email with the images downloaded. There's a hidden pixel that tells their mail system that your email address is valid. I believe all cell phones have some type of call blocking option where your phone won't ring, and if your landline phone doesn't offer that feature, just ignore the calls, as annoying as they are.

Answered the phone and no one was there, then they hung up

I would like them to stop calling.