Is there anything stopping people from just randomly filling in the surveys? It seems like the kind of thing where someone would have made a bot. How many people who are paying a couple of bucks for something like that are going to complain at you?
Survey instruments generally have a few ways to check for this, usually via attention checks which require you to answer in a specific way as stated in the question text (defeating your bot). Similarly a survey could be designed to ask the same or similar question multiple ways, and a survey response that lacks the expected correlation can also be rejected.