Anyone else having issues right now? I backed up my new phone to my 5S backup, and went through setting up the phone, touch ID, wifi, siri, etc. Still, the top left says 'NO SERVICE'.
Try going to www.att.com/activations and follow along there
That's what I did.I dunno how many people here are upgrading from another iPhone but doing the SIM swap before turning on the device worked great. Took maybe 5 seconds before the phone had a signal and was all systems go.