Wesbank - Bad customer service contact options

I recently bought a vehicle and received financing from Wesbank(***). My trade-in vehicle was also financed by Wesbank(***). The dealership that I bought the vehicle from contacted me after the sales agreement had already been concluded and I had taken delivery that they had made a mistake with the registration year of my tradein which affected the trade value. Because i refuse to pay in the difference of R40 000 as the mistake was not mine they have refused to settle the trade in. I now sit with the vehicle financing for 2 vehicles. I have since logged a query with Wesbank but have received no response. not even a reference number. How is the dealership able to do this? and if i default on either my credit scoring is affected. I want this resolved a.s.a.p.