Can't Swipe down the notification centre [Iphone 5]

I just bought it two weeks ago and what happened is that

sometimes I cant swipe down the notification centre and I have

to force restart the phone.

Is it the iOS or the hardward problem?

ALSO,

sometimes the 3G doesnt work, even though when i enabled the 3G

it doesnt shows E nor 3G.

I tested this situation few times in the same location and

by reseting the network

General > Reset > Reset Network Setting

the 3G became functional again.