SSI is probably Survey Sampling International. They are very large and have many telephone numbers, and thus there are many complaints on 800notes.
https://en.wikipedia.org/wiki/Survey_Sampling_International

They have a webpage with information on how to "opt out of getting calls from them" - it is worded to sound like they are doing this out of the goodness of their nosy corporate heart, but it's really because law and regulations require them to. Warning : after 5 years on their list, they can start calling the number given them again.

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.