My iPhone will randomly disconnect from the network, start searching, then say no service. I've tried airplane mode on and off, and doing a hard reboot multiple times. When I reboot it, it connects to the network, bars and 3G for about 5 seconds, then it disconnects and says no service. I pretty much can't use my phone. I am jailbroken and have messed around with the APN settings because I was getting "could not activate cellular data network" The APN settings work fine , until all of this happens.