As a rule Dish does *not* *not* *not* give refunds on annual programming. This is why there is a discount on annual programming packages. The HD - to - VOOM switch mentioned above is a special situation, but I've never heard of a sub getting back any money on a prepaid ATxxx sunscription.
Of course you can always ask, but don't act surprised when you hear NO.
Of course you can always ask, but don't act surprised when you hear NO.