Beware Uber driver

I have a situation where an driver working for Uber is keeping my goods randsom until I pay him a fare I never agreed upon. I am unfortunately the victim of a ******* and that is were everything started.

I was selling my 2 bicycles and the seller ordered the Uber driver. The driver was never paid and the buyer sent him back with my bikes. Apparently the trip was to cost R800, of which I have already given the driver R400. So now the driver wants the rest of the money before delivering my bikes.

I had nothing to do with ordering the driver and because of that I don't have any details for the driver except his car registration and cell no. I have no way of contacting Uber either.