I had to hand back a car early for health reasons and never got the GCB and didn’t know it was a thing if you cancelled before the 3 yr term. Would never have expected to receive it
As explained, you don’t get a pro rata refund of GCB, but you should have had a pro rata refund of your AP? Hopefully you did?
It’s also worth noting that if a car is returned early you don’t get any pro rata refund on the cost of any options that you’ve added either. That can result in a very expensive mistake for some people.