Unprofessional...no payment received after receiving vehicle and no response from we buy cars.1

A very disappointing experience with no payment received as yet. And we buy cars in possession of my vehicle with sales representative not responding to message. I recently sold my car to we buy cars. I explained to sales representative, that I am a doctor/ specialist on a very busy schedule, and therefore requested that we have paperwork completed before the day of sale. I sent through my documentation a week prior to sale. A few days before trade in, Jaynen Rania contacted me and said he has all my paper work needed.. On the day of the sale, the agreement was to meet an hour before the hand over of my new vehicle to complete sale of old vehicle. The sale amount agreed upon was then to be used as deposit on new vehicle.. I cancelled my insurance on old vehicle for 13 00 that day with trade in arranged for 12pm. I met with Jaynen and while completing paperwork informed me that the original Natis document was missing. I asked him if he had not gone through my documents prior to meeting and he admitted he never checked them ( witness can account). I then asked what would happen now as I needed deposit to make for new vehicle , and in addition my old vehicle was now not insured. He said that they could take the vehicle for storage and make payment as soon as original Natis was received. The sales gentleman who I had been dealing with Franco, kindly said he would drive to Investec and collect my original document. In the contract that was then signed and agreed upon, it stated that as soon as Natis original received they would pay me. My Vehicle was the taken. An hour later the original natis document was received and I asked for payment to be done. So I could proceed with payment of new vehicle.Jaynen then said that he would not make payment as there was a missing BRN document. I am furious, its been 3 days and I have not received payment. The sales representative are not responding to my messages and this matter is unacceptable I wish to have my car returned to me if no payment is to be made , yet nobody is responding to me