Undervalue cars to be auctioned, bad services

We received a sms from Wesbank on the 13th of October, regarding our car that we surrender on Thursday the 12th of October at 9 am, here in Gauteng. The sms state that we should call Diana Theunissen (Team Leader) at *** (located in Cape Town), as she values our car at R70 000 to be auctioned. While we still owing the bank about R226 000 and the book value of the car is R230 000. How is this fair and we are not able to get a hold of her, she did not even see the car. The Mazda CX-5 was advertised at PB Motors and we have a potential buyer. The buyer made contact with us on Thursday the 12th of October (late afternoon) to buy the car for R210 000 more or less. We surrender our car in good faith to Wesbank and now they are going to place us in an impossible situation, regarding the remaining debt that we can not afford. It feels like we are being ****med.