Somebody trying to sell personal medical alert systems to seniors and claiming that somebody had referred them (automated message). At the end of the message it says press 9 to opt out. Not sure if it works, but I tried it.

This is seriously getting annoying.  I get one a day every day and I am on the do not call list.  They never leave a message, if I answer, there is never anyone there.

This is the second time that these annoyng scumbags have called.

Answered , no one there.

Understand that the "No call list" only applies to legitimate businesses. Scammers and crooks regularly ignore it. Robo call devices are the most valuable tool of these people. Their robo caller initiates calls using a bank of several phone numbers (some of which don't exist).
1. Have a phone providing Caller ID. If you don't recognize the calling phone number, don't answer. If you have phone recording facilities and the call is legitimate, the caller will leave a message. Scammers usually leave no message.
2. Do not press 1 or 9 expecting to be removed from their list. This action only alerts them that yours is a live phone number. Do not answer or respond to the call in ANY manner.
3. Purchase a call blocker or a phone with caller ID, voice recording facilities, and call blocking facilities (many DECT 6 phones have all these).
The equipment to fight scam calls costs in the range of $50 to $100. It is worth it. There is little that state or federal governments can or will do for you. Believe me, the above suggested equipment  really works.