What they do is contract a company that a registered charity or political to do the survey. The other way to get in it for a company that you have done business with to sub contract to another company so you have legally done business with them.
Several years ago, before the do not call list, The small mortgage company we were with was bought by Wells Fargo. After a few months the sales calls started coming and I'd tell them to put me on the do not market list. Then in a few months they would start again and I'd repeat put me on the do not call list. In a few months the calls would start again. I finally worked my way up the manager chain from the caller and found out that if you tell a subcontractor such as "ABC marketing" to not call you that only applies to "ABC Marketing" and not to Wells Fargo even though they were calling on bahalf of wells fargo. So wells would change the subcontractor ever 6 months so you had to get on a different sub contrator's do not call list. So I then called up wells and told them I wanted to be on their list which stopped it for a while until they started calling from their collections department which was legal then since it was initated as a collections call and not a marketing call but since we have you on the line would you liek to buy x. Now before you tell me I shouldn't have let me account go to collectios, I didn't, their system could call me and when I finally got a person the person would see my payment posted days before, what they would do is recive the paymentm, then sit on it for several days and then finally apply it. Back in the days of checks its reasonable to accept a check and hold it for a couple days to make sure it clears then post to your account but I paid electronically and thay delay started stretching pact 10 days from the tme they recieved my payment to the time they paid it. So i could make a payment on the 20th that was due on the 1st and by the 30th their collections department would be calling me. Making a payment ahead didn't help anything either because they would just apply it to excrow and balance instead of counting it as an extra payment.
It was satisfying though when we sold the house and moved to be able to call them up as if I was going to apply for a mortgage on my new house and instead tell them I would never do any busines with them again due to the way they treated me.