No, they did not.

Scammers will say or do anything to gain your trust, and pretending to be part of the 500 Casino Staff is one of them.
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If someone adds you on Steam and says they're part of 500 Casino, you should stay cautious. Don't click any links, don't give away any information and don't send them any skins.

If we need to contact you, we will do so via the official channels - We will either send you a message inside the Support application or it will be in reply to an e-mail that you sent.

Stay safe.