After the Apple press conference/Phone industry mocking event last week, Apple’s iPhone 4 Case Program has begun in earnest. The program provides a free iPhone 4 case for any user who wants one, in an effort to mitigate the device’s signal loss problem. iPhone 4 owners who have already bought a Bumper from Apple or AT&T can get a refund, while those who haven’t gotten one can choose between a free Bumper or a selection of third-party cases.

For current iPhone 4 users who want a new Bumper or other case, you’ll have to download the iPhone 4 Case Program app from the App Store. When the app launches, you sign in with your Apple ID, and you’ll be presented with a selection of cases to choose from. Currently you can choose either a black Bumper or one of seven cases from InCase, Belkin, Griffin, and Speck.

The app notes that “case availability and selection may change,” and Jobs said during the press conference that there won’t likely be enough Bumpers for everyone who bought an iPhone 4. If you’re having antenna problems in the meantime, though, you’ll have to wait a bit for this current solution—cases ship in 3 to 5 weeks.

If you purchased your Bumper via the online Apple Store, you’ll automatically get a refund. Credit cards will be automatically credited, while those who used gift cards will be mailed a gift card for the refund amount.

If you purchased your Bumper at an Apple retail store using a credit card, Apple says you should get an automatic refund . If you used cash, check or a gift card, you have until September 30 to bring your receipt in for a refund. If you bought one at an AT&T store, you’ll have to fill out and mail in (by September 30) a rebate form to get your refund.