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Could you tell us more details about your scenario? If you want to know about PlayFab login, you can refer to https://learn.microsoft.com/en-us/gaming/playfab/features/authentication/login/login-basics-best-practices for more details. And PlayFab provides the player ban feature (https://learn.microsoft.com/en-us/gaming/playfab/features/playerdata/player-bans) which allows you to restrict access to the game for certain players who break the rules. In addition, PlayFab also provides a C# example of logging in using LoginWithCustomID (https://learn.microsoft.com/en-us/gaming/playfab/sdks/unity3d/quickstart#making-your-first-api-call) which you can refer to.