It doesn't matter, I doubt it was a legitimate survey.
I think it was a pitch for contributions, and an ad disguised as a survey is legal for calling someone on the do-not-call list. (You would not believe the blatant marketing spam I get, dressed up in "survey" livery.) As soon as they realized they weren't getting any cash out of me, they went away to prey on someone else. I just hope they deleted me from their call list, or don't sell my number to somebody else.
Next time, I'll be ready. I have an effective defense for this particular kind of home invasion.