Not getting text notification- iPhone 4?

Hi so I recently got an iPhone 4 and all was going good until yesterday. I don't get notifications unless I'm actually in the text app. My phone doesn't make a sound or vibrate?

IPhones are known for having problems like this. There's no way to fix it, but the best advice I could give to you is go to the carrier you got your phone from and they will probably give you a new one for free. But all iPhones are bad for this, even the new ones. I actually think they are quite overrated. I had similar problems with my old iphone 4