For some odd reason in my house i will constantly drop from full strength/bars to "No service"/no bars. My iPhone will remain with no service usually for serveral minutes. I have tried restarting and it still have no service after booting back up. only after several minutes will it come back. When this happens i have compared to another att phone side by side and that phone has full strength and never drops out while at my house. This is my second iPhone and i had the same problem with my first iPhone. Any thoughts on this issue?