My daughters iphone 4 has been dropping it's 3G coverage randomly for no apparent reason even though we're in an area that has great service. Instead of the normal "3G" service on the top of her screen she gets a little "O" as if there's no 3G available. With this she's still able to make calls but data won't work. It happens in all locations, not just at our home. Any thoughts? She tried the *228 but that didn't help. Thanks for any idea's.