iPhone “Waiting for Activation” message

If you have followed all the instructions that come with your new iPhone, only to be faced with a “Waiting for Activation” message that remains unchanged for hours, try powering the phone down completely. Press and hold down the Sleep/Wake button on the top right corner of the phone until the red “slide to power off” slider appears, then slide the slider. To power it up again, press the same button until the Apple logo appears.