Why does my service/internet stop working on my iPhone?

I have had an iPhone 4s for 2 years, and never had any problems until the last few days. I can't text, call, or do aything that involves my 4g service. I have to turn off my iphone completely and then turn it back on. Sometimes I have to do this 4 or 5 times until i can text/get on internet. And when it does finnaly work, it will only last for about 5 minutes. Then I have to restart it again. This is very annoying and what can i do to fix this?

It may be due to configuration settings.

Settings-General-Reset-Reset Network Settings. If that doesn't help contact your carrier.