Truth is generally the best vindication against slander.

Answering a lie with noise usually spreads it, since the denial carries the accusation to people who had not heard it. The steadier defence is a record: what you actually do, over time, in front of enough people that the story stops matching the evidence. That is slow, and slowness is the hard part when something untrue is being said about you right now.

Resist the urge to fight it on the same ground. Correct it once, plainly, to the people who matter, and let the rest be answered by how you go on behaving.