recently my iphone has been dropping signal a lot more often than it did before. i noticed it after the 1.1.4 upgrade. i can be standing in one place and the signal will drop to one bar, and then to No Service. it usually doesnt gain signal back unless i switch it to airplane mode and then back again. also every so often it says that there is no sim card installed the only way i can get rid of that is to reboot my phone. then its usually fixed. so i was just wondering if i took it to an apple store if i would be able to get a replacement, only problem is i have a 4gb, would they have 4gb's to give me as a replacement or would i have to upgrade to the 8gb?