As a Coach, you are able to delete clients both from the Coach Dashboard and from within the Ate app.
From the Coach Dashboard, tap on the specific client > three dots at the top of profile/stats > remove from clients.
From within the Ate app, tap on Connect > My connections > select client > Profile > Connection settings > Disconnect.
Please remove any inactive clients from your client list to be able to stay within your chosen client subscription package.
Once you disconnect from a client, then they will no longer be able to access Ate for free, they will need to choose a subscription if they decide to continue to use Ate on their own.