Unpaying client

Halp please.
After 4 years of successful freelancing, I only now have a client that won't pay.

The bill was €2200, due 30 June 2018. The client promised to pay by 31 August after I had a lawyer write a letter to them... and now it's 16 October and they still haven't paid. They haven't responded to a bailiff either.

Now I have lawyers fees (approx €500) for this service, meaning I'm really losing out.

How can I get this client to pay?

Can I report them somewhere for being a terrible business?

The client is a small Brussels-based grant writing business.

Any tips helpful!
Thanks!