guys,need help

recently i bought iphone 3gs for my fwen. but a week after using the phone, it got power ic prob where it unable to turn on. so i send d phone back to the shop where i bought. now it's a month already...still not fixed

the prob now they claim that the phone unable to charge.i already fed-up and try to make a deal to switch over to a new iphone4. they said they'll investigate the phone i bought 1st whether does it worth to switch with ip4 and top up some more.

i really dissapointed as my fwen use the phone less than a week and they seems to refuse the switching deal. if lets say the phone is totally bricked and they dun want to switch, i'm totally f**ed up!

**it's an ap phone**