"the band" case from gear4 causes stains on iPhone 4

After using for 4 months "the band" case from GEAR4, my iPhone 4 got stains all over

the metalic antenna!! I 've contacted the GEAR4 company, sent them detailed photos,

but denyied the responsibility. They said it's APPLE's fault! As if we dont

know the quality standards of apple products! Has anyone had this problems?

Any suggestions what should i do?