Under normal circumstances, that generally means Social Security. In this case, it is a survey company that is using the same initials. SSI Survey Sampling, a marketing research company.
Keep in mind that if they do not place you on their internal DNC list, they can still get into trouble. As a rule, survey's are exempt from the DNC though. Do consider maybe getting a call blocking device or phone.. You can google them and many are around $40.00 or under.If its a cell phone, some already have call blocking, if not, there are free apps on the web that will work for some. You can google this. If you have a smart phone, there is a free app called call control. Iphones appear to have apps also. Another one is called Mr. Number.For tracfone & straight talk:
Charities, along with some Survey's and Political calls, are exempt from the DNC, however, they can still get into trouble for not placing you on a internal DNC when asked, you can also check your states laws in regards. Some states have different laws in regards to the calls, which can differ from the federal.