If there's anything to gain with these "surveys", it'll end up costing you far more than you will get from it. Mostly, they're set up to get personal information, with nothing awarded but junk mail or spam emails.
Asked if I could hear them - after reading an article about how calls like this are looking for me to say 'Yes', I was suspicious so I said "I can hear you" to each response till they hung up. fishy fishy.