There is usually an agreement or contract when buying a card. Please see if the above terms are beneficial to you, such as the service provided by the gym. Besides, are there any requirements for returning the card? If there are clear terms, it will be easy. If not, you should "influence" them with perseverance and talk to the manager every day ... pay attention to protect yourself, don't conflict with them, and be careful to prevent "blackness", you know.