So sorry to see this injustice done, but this is Ebay, nothing unusual  or unique for this happen.

Not only that buyers lie & damage your reputation, they also trash your stars, so easy to do as there isn't really any practical ways of making them accountable for their actions.

But whatever you do, please resist the temptation to "give them some of their own medicine"

Don't worry, someone is going to do it sooner or later (always happens) without you having to take the dubious "credit" for it.

Also, you'd be surprised as to how really helpful Ebay is these days about unfair f/backs, it would pay you to ring them. They consider not just the comment but the correspondence before & after.

Good luck, stay well,

January.