Incorrect vehicle registered

I sold two vehicles to Kia Kempton Park and bought a Sorento in September 2015. The 2 vehicles sold to them was still registered in my name in Feb 2016. The incorrect Sorento was registered in my name and I already received three speeding fines and Toll fees for the sorento and one of the other vehicle that I sold. I am back on paper plates for the Sorento for the last 5 weeks. I have been told that the fines and the toll fees have been paid but they are reluctend to send me the proof of payment. All that I get from Kia Kempton Park is promises and appologies and I am sick and tired of this type of service. I will be launching a complaint to the Motor Industry Ombudsman as this is totally unacceptable!!!! No one wants to take responsibility.....