Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_5 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8L1 Safari/6533.18.5) So I live in an area where I have great AT&T service. 4-5 bars usually. But sometimes my entire cellular signal drops n iPhone let's me know "cellular activity unavailable". N then a few seconds later the cellular signal is found again. Is this an AT&T issue or an IPhone issue?