apple store how can u refuse to repair my ip4 within one year warrantee iPhone 4

I live in shanghai, bought the ip4 from apple online store China since Dec last year. 3 days ago found my phone completely lost singal, but voice receiver,wifi, micofone, touch screen works normally, i think maybe something wrong caused by software. so i try to restore my ip4 via iturns & fix it. but after recovery found the problem still exsit, and can not active any more. so i went to Shanghai Pudong App store search for help and fix this problem, but after your after service dept unpack my ip4, they told me refuse to repair because they found my ip4 unpacked before, and one screw missing, one water-protecting stick damaged! im very suprised and very angry, i never and ever open the iphone cover beofore! more important, my ip4 now under one year guarantee! need i dismount some element before the normal way to fix my phone? how can your after service pass the blames to your clients?!? more funny, when your after service took out the battery & check the main board they found the series no. is different from sim card slot and your e-invoice!!!! that i start to doubt if your apple online store sold me a reworked ip4??? pls givme a reasonable answer!!!! or else i will find some leagal way to solve this problem, my contact: zhufeiyu@yeah.net mobile:+86 13611772249. awaiting some postive reply...
iphone 4 iOS 4