How can you prevent review cheating?

Question

Survey tools

Asked a question here.
What I have thrown so far:
Firstly, from one phone number you can leave only one review for a specific user (1 to 1). The ownership of the number is checked by the SMS code.
Secondly, delete (or simply flag for everyone to see) suspicious reviews. But do not punish, because there may be cheating from a competitor in order to punish the victim.
Thirdly, to prevent writing a review from one ip/browser/computer.
What else can you think of?
Because the service is strongly tied to the rating, and reviews play the biggest role in it, then a person may not be stingy with cheating reviews (order sims from some thieves).
UPD: came up with another: because. a review can only be left by a person from the same city (there is no other way to use the servant), then you can check if the number belongs to this city (I think this is possible) and, in case of discrepancy, automatically mark the review as suspicious. In case of accumulation of such incidents, send the user to the moderators for verification in order to clean up the "dirty" reviews.

Answer 1

this protects against the average user. a professional will bypass it without problems. several hundred sims for one person are not uncommon
to be tied to a credit card / payment. it's harder to screw it up.