Why won't my iPhone 5c charge normally?

I've bought a brand new iPhone 5c 16gb and when it was charging it had the lightning bolt symbol next to the battery and even when it was 100% charged the usual plug icon did not appear. Why was there no plug icon?

I had left it on charge for 8 hours and the lightning bolt was still on there

Shut it down and restart it. Maybe it's just a glitch of some sort.