You are correct. Also most political organizations and charities
But my point was this makes them no less annoying. Right?
Call blocking doesn't work because they called back from a different number the next night.
Anyway, if you call them back they will give you the following email address to request an opt out -- provided you add your telephone number to the body of the email.
[email protected]
Their website:
https://www.surveysampling.com/contact/opt-out-do-not-call/