Apple has started refunding Bumper purchases today and will continue doing them in batches throughout the week, according to MacRumors forum poster Chodite.
"Just got off the phone with Apple and they said that those that purchased with debit cards should see a refund in 6-8 days...credit card refunds will be by the NEXT credit card cycle... refunds will be AUTOMATIC. Also, those interested in the "free" case, there is no estimated date on when that will go live but she said that information will be made available on Apple's site when it goes live", posted web4fun.
Apple has also begun sending emails to those who await shipment of their Bumper to let them know it will be free.
If you had already ordered then you will receive an email saying that you will not charged.. a link will also be there in the email showing your order status.. thats how it was for me..I checked there and I was only charged for the iphone 4..