With the help of a Google search, try to find an address that belongs to the unwanted number. If they have a website send them an email stating that you have received numerour unsolicited phone calls from their company and that you have politely asked their agents to put you on their "Do Not Call" list, but this information has fallen on deaf ears. Tell them this is request # 3 and that they do not have permission to call you. List your phone number. Then simply state that if you receive further calls from that company that you will file a claim with the FCC and then follow through on that threat. Don't just threaten to notify the FCC, get a claim number from the FCC and hold them responsible for their jobs. This has worked for me. I finally got Hilton Grand Vacations to stop calling me. I used to receive 2 & 3 calls a week from Hilton Grand Vacations btu haven't had one since July 17 - so far so good.
I also have an FCC file number against 877-875-2668 that says "Stop whatever you're doing and listen to this imporetant message...."
The only way we're going to stop these incessant pesty calls is to follow through on our threats. They're like children, you can threaten all you want, but they'll never change their ways if you don't carry through on your threats. Period.
The discussion concerns a debt collector, not a telemarketer. The rules and countermeasures are different. Debt collectors are *always* "unsolicited* and they don't typically maintain any "no call" list. At most an individual account file might be tagged with instructions, which as "work product" will not travel if the account is resold or reassigned.
The CFPB and FTC have primary federal oversight of debt collection, not the FCC. We have a 35-year old law which grants the right to limit or ban all forms of debt collector contact. That's what you study and use if you don't want your demands met with derision and chuckles.
FTC and CFPB material on US federal collection law:
http://www.ftc.gov/os/statutes/fdcpajump.shtm
http://www.consumerfinance.gov/askcfpb/search ... debt-collection