Hi
The Silicone Case is covered against defects in materials and workmanship under Apple's One-Year Limited Warranty.
If the case fails under normal use, contact Apple Support (mail-in service may be available), make a Genius Bar reservation or visit an Apple Authorised Service Provider with a view to having it checked and, if agreed, replaced under warranty:
- Contact - Official Apple Support
- https://twitter.com/applesupport
- http://www.apple.com/retail/geniusbar/
- https://locate.apple.com/
Note that the warranty does not cover accidental damage, nor does it cover damage caused by misuse or using the case outside Apple's guidelines.
I'm afraid that no-one here can tell you whether Apple will exchange your case (this is a user-based technical support community).