You can call or email them, and they'll process a warranty replacement. But, it takes FOREVER! I'm still awaiting delivery. It's been two weeks already.
I have had 7 of these damn cases now and only had my phone since march! They bust at the clips that hold the two halves together as well, I have also had a replacement sent to me with a busted screen protector on it. They have a good warranty service but they need to make their products with better quality. I am seriously considering running naked as my front and rear glass have scratches on them due to the horrible non dust proof design of the Otterbox I am not impressed.
My Defender case is stretching out also and it's only a week old. My last one was too loose and the store said it was defective so they swapped it out on the spot, it went on tight but now it's getting looser.