@Type_93 Reymu is correct:
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A player entering into a battle and intentionally deciding not to play can result in temporary Game Bans that can escalate to permanent if the offense is repeated.
Please create a Customer Support Ticket and include the Replay of the battle. Use "Collusions" as the reason due to the player's decision to "help the enemy team".
https://na.wargaming.net/support/en/products/wows/help/31336/31337/31338/31339/