Shartfall claims

I joined the shartfall insurance with them for the car and when they supposed to pay the shartfall to the bank they paid half and they said the other amount should be paid by me, as in I'm still confused how? Because I joined them with the understanding of that if anything happened to my car the insurance will pay the market value of the car and them will pay the outstanding amount (shartfall) to the bank, and all of that has twisted.