According to the non-answer I got when I questioned my US Senator, apparently forever. My solution?
I bought a 'call blocker'. Search with Google, and you'll find one that is suitable to truly handle this constant badgering by phone that the government passes laws to stop, and then does nothing to do so.
They pretended to be my credit card company but never gave their name. Because it came from Kirkland, we thought it might be our son, as we weren't sure about the number. I listened; never gave them any info and pressed 2 to not be called again. Said they could lower my interest rate to 6.9%. Because we have a Costco/Amex card combined, think they were trying to pose as such. Should be reported but don't know where. A true scam. They just want your CC number.
Didn't answer the call while on a business call, but it has to be a scam. I don't have any business in Washington state, don't have any debt, and it calls my business cell phone which isn't even tied to my name. Someone obviously got a number list and it robo calls all the numbers.