Case by a company after failing to provide its services or return fees

I paid a company AED 5000 by cash deposit into their bank account as an initial payment for a job that they didn't do. So I contacted them to refund the payment telling them I will file a police case against them.

They started stalling until they stopped answering their mobile phones and stopped responding to emails, so I asked around some common work acquaintances for their address or if they know anything about them.

I received an email two days ago from them showing they filed an online case for slander and other claims that are pure lies against us as well as demanding compensation, it has a reference number...etc.

I want to know how to deal with this because all their accusations are pure lies, they filed it as a way to escape from paying my AED 5000 back.

I want to know the procedure and the steps to solve this.

Thanks