Greetings, Colonel.
Short of a law that that Chemlawn may or may not be violating, TURN THE TABLES.
I, too, used to dread these calls until I turned the tables.
Several versions:
Tell them that whoever they asked for is home, out in back in fact dealing with some lawn issue, please hold just a minute, I'm sure they will want to talk to you. Stretch it out, returning to the phone the first time to say he's coming, then to say he thought I was kidding since he was just saying how much he hates to do yard work, then needs totake off his shoes, etc.
Tell them in no uncertain terms, after confirming thatthey are ready to take down a message, that you are not interested in whatever they are shilling, even if it is free money.
Many people mistakenly think that by hanging up on the machine before a person comes on that they are acomplishing the same, they are not. The machine that dialed your number thinks an answering machine has hung up on them and you go to the end of the line to be called again later.
Tell them that whoever is home, but that you refuse to bother them with a shitty telemarketer, that you always answer the phone, and that they will never get to talk to that person.
Ask for a number to call them back later.
Etc.