Shortfall cover not honoured.

I bought a car in 2012 at VW and i was financed by Wesbank at which i also took the shortfall cover Plus at which by August 2014, i received a mail from Wesbank stating the shortfall value i have for the car is R26771.49, as the years went by in june 2017 i was involved in an accident at which my car was written off and it took two/ three months for the shortfall division to give me feedback after a series of phone calls i made to them, the worst part is on the total amount of the cover i had for the car they only paid R686.32. My question why was i paying for the cover if they were not going to honour it, now i owe R25970.28 and how does that happen??? because am not willing to pay that money. please assist.