Many telemarketing calls like this originate offshore to skirt the No Call List. And that's why, if you DO speak to a person, you can't understand them. They use VoIP to make (literally) millions of calls, and make it very difficult to track down. According to a story on NPR the week of 12/21, the feds recently were able to close down one of these, but there are many others.
Not sure what the low-tech/no-tech options are, other than having a machine screen all your calls. Perhaps your outbound message could be, "Sorry I can't take your call, but due to the number of telemarketing calls, I am no longer willing to answer the phone. Please leave your name & number, and I'll call you as soon as possible."
I have been getting many calls from many different numbers, this went on for months. I finally called the F C C and complained. The lady at the F C C took some numbers that I had saved and said they could do nothing on an individual basis but if they got enough complaints they would look into it.
Maybe we need to bombard the F C C to get them to do something. I have tried talking to the phone company and they say that they can't do anything. I am tired of paying good money for phone bills to have to listen to these calls.
I did receive a letter from the F C C It was signed by a Sharon C Bowers. The number to call is F C C consumer center toll free 1 888 225 5322.
Please call it only takes a minute or two and may do some good.