No-Show dispute

Hello Community,

I am not sure if we are alone with this issue but I could really need advise.

We receive multiple reservations (fraud) for people to enter the country (annoying enough) but now they started to dispute to booking after we marked them as no show - booking is requesting proof from us that the guest did not show up. question: How do you proof that someone did not actually check in?

And how do you protect yourself from incidence like this?

Advise is really needed here as the number of those cases is rising and we spent most of our time discussing with booking.com regarding unjustified commission charges and proofs that simply cannot be provided.