Does the fitness instructor need to pay back the money he was cheated of?

You don't have to pay back the money cheated by the fitness instructor. According to the relevant information, this is obviously unfair. We can negotiate first. If negotiation fails, you can collect evidence of fraud and call the police. Report to the Consumers Association or the industrial and commercial department. If it still cannot be solved, you can file a civil lawsuit. You can also file a civil lawsuit directly without consultation.