Cancellation of contract

I have cancelled my car insurance (Policy No: ***A) with Bidvest in the middle of June as i have sold my car. They have deducted the money (R349) from my account in July and August. Now when i called the Durban branch to enquire about it, the lady (Ronnel) tells me that is should have called the under writers (IUA) and not Bidvest directly cancel the policy. Can someone please assist me as its unfair that I have to incur cost for something I don't have any more.