SSI is possibly Survey Sampling International
https://en.wikipedia.org/wiki/Survey_Sampling_International
a very large survey business that has many telephone numbers - and thus many complaints about unwanted calls on 800notes.
Their website has an "Opt-Out" page
where they say they will stop calling your phone number out of the goodness of their nosy corporate heart, but the real reason is because federal law requires it.

https://www.surveysampling.com/contact/opt-out-do-not-call/
We appreciate your participation in our research and we value your opinion. But if you do not wish to participate in future surveys, we understand and respect your decision. You may choose to opt-out through any of these means:

Email us at [email protected] and include your phone number in the body of the email.
Call 1-866-360-9563 from within North America or 1-801-379-4094 outside North America to be placed on our no-contact list.