Halo reach wont read certain maps and levels?

I have had halo reach like 2 weeks or so and i have brought the game back to gamestop 3 times with the protection plan. It freezes and says disk is unreadable on the map Powerhouse and at the end of the 3rd mission on campaign. This occured on all 3 disks that i owned. I have called micrsoft and they are clueless ne know any thing about this or have had similar problems? Plz Respond!