One thing that I find useful is to look at the about page, as well as terms of service or privacy policy, of any website.

If there's no entity named, or you can't verify that a named entity actually exists, it's a red flag.

In this case, there's no individual or company named anywhere that I can see. Not on the About page, and not in any of the legal agreements. And the phone number looks like it's a VoIP number from Onvoy, a major wholesaler, which is a yellow flag.