8 months left on the policy and I pay for it monthly
This is one of the little traps of the insurance industry.
While you might think you're paying for your policy month-by-month that isn't what's happening. Actually the insurance company (or, more likely, their credit brokers) are lending you the full premium at the start of the policy and you're paying them back over 12 months.
So when you cancel your policy the insurance company's T&Cs determine how much of a refund you're due, but you still have to keep repaying the loan until you've paid back what's due.
As most insurance companies don't operate a pro-rata refund rate it's quite common for cancellations to leave you due no refund at all, even if there's still quite a lot of the policy left to run.