I'm not sure I know exactly what you are asking but my assumption is you want to know how to prevent the gym's form stealing your clients. There are plenty of ways, such as contracts, personal relationships, make your own app that the client pays through. However, if you are asking how to prevent them from stealing your client, the dead honest answer is you don't. You provide your clients with so much value and create a very personalized service that they don't see the gym as a value but your service.

If I didn't understand what you are asking, please reach out to me for some clarity and or so I can help you!