Survey companies are exempt from the Do Not Call list. Many scammers hide behind that loophole and phish for information.
In the case of SSI, the Better Business Bureau ( www.bbb.org ) lists three sites for BBB. It appears that Survey Sampling International, LLC 3300 N Ashton Blvd Ste 350 Lehi, UT 840435351 is the business to complain about. They have many complaints, and it appears that they promise to remove numbers from their database.
I highly suggest you file a complaint. I did on another company, and it eliminated further calling.
Calling with political survey but barely spoke English. Seemed like the survey was designed by a Portman supporter. Trying the opt out, will see if it works. Called for weeks and did not answer but yesterday my son answered.