The cheapest defence: publish an official-channels page
One page listing every legitimate domain, profile and support address you operate. It costs an hour and defuses a whole category of impersonation.
Most impersonation succeeds because a customer has no authoritative way to check. They receive a message from an account bearing your name, and the only thing they can compare it against is their memory of your brand.
An official-channels page fixes that asymmetry cheaply. Publish a single page on your primary domain listing every domain you operate, every social profile that is genuinely yours, every support address you send from, and — just as importantly — a plain statement of what you will never do. “We will never ask for payment by direct message” closes more attacks than most monitoring tools.
Then link it from your support correspondence and your email footer. When someone is unsure, they need a destination, not an instinct.
This is the first recommendation in a large share of Guardian reports, and it is the one customers most often implement the same week. We are telling you here because you should do it whether or not you ever buy anything from us.