SSI is Survey Sampling International and there are many phone numbers they use, and thus many complaints on 800notes about them.
https://en.wikipedia.org/wiki/Survey_Sampling_International
The website has an opt-out page :
https://www.surveysampling.com/contact/opt-out-do-not-call/
*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.
They try to make it sound like they are doing this out of the goodness of their corporate hearts (and the corporate hearts of the unidentified corporations that pay them to be so nosy), but federal law requires businesses like theirs to have their own internal Do Not Call list.
They just don't want to say that, or use the phrase "internal do not call list".