Hi All, After pre-ordering and picking up the iPhone 6 on launch day with 16GB storage, I've decided to pick up an iPhone 6 with 64GB. My plan is to order an iPhone 6, 64GB early tomorrow morning at a store close to me as long as it's available. Then, I'll go in with my current iPhone 6, the box, etc. Can I return it, pick up the 64GB and pay the difference? Or will I return it, have the amount credited back to my account, and then just flat out buy the 64GB? Just want to make sure this all will work. Thanks!