How to get telemarketers to stop calling and being rude?

I have joined the National Do Not Call list from the website https://www.donotcall.gov/default.aspx but I have to wait until after 31 days to file a complaint. I have asked this company to take me off the call list and I have called them back and used the prompts and selected the take me off the list option. The last time they called I hung up and the guy called back and was calling me bad names and said f*** you multiple times. I'm so tired of it. I can understand if it was from a bill collector or something but this guy is only trying to sale me stuff. How do I make it stop, some days they call multiple times and I can't stop it. They did tell me that I qualify for a Wal-Mart gift card for only the cost of shipping $2.99, other than that there's not a lot I know about them. The phone number they call from is 302-394-6908 Any suggestions will help, I'm desperate.