I was getting calls like this, but it was from an 800 number, and I put their 800 number into the auto-dialer in my computer, and went to bed. All night long, about every ten seconds, my computer would call their number and they would answer the phone. Of course, they would find no one on the line, and would hang up. Immediately, then my computer would dial their number again.
An added benefit (since it was their 800 number) is that they are charged for each incoming call.
I used to get repeated calls from a bank wanting to sell me credit card insurance. I repeatedly told them no and finally got sick of them calling. I called them back and tried to sell them my old PC. I did this about 6 times before a manager got on the phone and tried to tell me off. I told him that if he (the bank) was going to call me I would return the favour ten fold.
These folks are calling my elderly mother several times a day...she is on the Do Not Call List but they continue to harass her. No one ever says anything and when you call the number back no one answers the call. I have filed a complaint with the Do Not Call List, but they don't act on an individual complaint, only after a group of complaints. Sad situation!