From my experience, they will continue to call whether you answer or not. Your number is on the a cheap list of telephone numbers and you get called for all sorts of crap. Ive had this going on for five years and havent found a way to stop it
Here's the thing. If you don't answer, the computer will automatically call you back. If you answer and hang up, it's marked as a 'disconnect' and the computer will call you back. If possible, have a nice little chat with them, say 20-30 minutes or so. This has two effects: your number isn't dumped back into the call-back-ASAP queue, and you prevent the telemarketer from making a sale for a period of time. There are articles from telemarketers that document exactly this effect.
Telemarketers can make up to 10 millions calls/DAY (or more). They are completely unable to answer 10-15 million calls/day. If people realized that we grossly outnumber them, and took advantage of our numbers, we could effectively wipe out telemarketing in months. If only 24 people answered the telemarketer, and talked to them for 20 minutes - that's 1 sales agent that makes no sales. Thing of how few people out of 10 million calls it would take to completely disable their call center. Don't think of it in terms of how much the sales person is making for talking to you, but for the lost SALES the company is suffering by talking to a false lead.
Also, for many telemarketing campaigns, the company managing the robocall campaign is paid by the end-business for EVERY 'qualified lead'. So pressing '1' and getting connected to a person for 10 seconds can cost them $2-$3 for each call. That could cost them $500-$1,000/hour per line, so it's definitely worthwhile.
Telemarketers can only make money by having a human on the phone close the sale. By talking to them, you are restricting their access to those sales. No sales, no profit. No profit, they can't afford to telemarket.
Everything the FTC and Telemarketers tell you (i.e. don't answer or hang up) does nothing to help stop telemarketing. It actually maximizes their time, resources, profitability by preventing them from talking with worthless leads.