Iphone 5s keeps losing service?

I got my iphone 5s about two weeks ago, it was a brand new phone not second hand, I haven't dropped it and there has been no damage to it. When I first got it everything was fine but yesterday and the day before it wouldn't allow 3G to work and it Kept losing service, we aren't in the country side or anything so service/signal/internet is never a problem.

Any ideas what it could be or any ideas on how to prevent it?

Your carrier is probably having problems