Poorest customer care service I have ever experienced

I am so frustrated and disappointed. We finished paying off a vehicle more than a year ago. We never heard from TFS again, now we are in the process of selling the vehicle and we require the Natis papers, which they never sent or contacted us about. We then asked for the papers and they were kind enough to say that they will put it on my husbands name and then send it within 10 working days. We did the payment and then just nothing. Nothing, no reply, no feedback, no Natis papers. It has been more than 15 days and they just keep on telling us we will get it but we dont. The person to whom we are selling the vehicle has been waiting for 3weeks now. Every person that we contact tells a different story and no one helps us. We are so frustrated, I am truly sorry that we have another vehicle that is financed through them as I have never come across such poor service. We are also unable to pick up our new vehicle as a result of this delay.