Lega Advice Needed (Brussels)

I really need some legal advice. I took a car out for a test drive from the BMW garage in Evere. I returned the car (undamaged) and gave back the keys. Then 30 minutes later they called me to say that I had crashed the car and there was damage. Now they are demanding that I pay for the damage. I just want to understand where I stand.

Any help would be greatly appreciated.