Poor service

I bought a vehicle in March and while signing at the dealership i was sold a warranty with Msure which is included in my instalment at Wesbank. I cancelled the warranty because it was misleading. I have the cancellation confirmation from Msure. I sent this confirmation to Wesbank to adjust the installment as i no longer have this product and Wesbank keeps sending me to the dealership. The dealership told me they cant adjust the installment because its done at the bank. No one is taking responsibility and i feel i should not be paying for something i cancelled. My installment is not being adjusted and no one is assisting me.