He needs to make sure he removed permission for the game to have access to the phone data ect... Before he delete the game go to apps clear data to game. That should remove everything if he does the steps
I am afraid the question as is is not really precise.
The answer from @Kimber is how to delete data from the phone/tablet. Reinstalling the game on the same phone/tablet will re-fetch the data.
I assume the user is asking how to delete the game data from the Playrix server and that is why they contacted support? I am surprised by the comment that nothing was deleted. If Playrix has deleted data, then the game should be reset to level 1. If that didn't happen, contacting support is the only way to get the Playrix personal data removed. If the bot doesn't respond, contact support directly https://playrix.helpshift.com/webchat/a/township?l=en&p=web