Why am I paying insurance on a car that is written off?

I pay my car insurance via monthly direct debit and my policy started in march 2007.

My car was written off in June 2007.

I have just received my settlement cheque and the broker has taken £280 out of it to settle my outstanding premium to March 2008.
Is this usual practise?
Why am I paying insurance on a car I don't even possess?
Aren't I entitled to a rebate and, if so, how do i go about this?