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I don't recognize any of these accounts.
What about using other people's devices or ISP to access the website? I've also seen cases of people being accused of multi-accounting because they used other people's devices or ISP to access the platform.
Regarding the "threat of legal action", it sounds like just a generic response they put in emails like this after making a decision about a case. Anyway, if you are not satisfied with their decision, you could try posting this on casino.guru. They are listed there, and I checked some of the cases they have there, and from the looks of it, they do respond to casino.guru staffs.