What is the circle at top of my iphone 4s how do i fix it?

Ok i just got my iphone 2 days ago and the internet is barely working. Well the main promblem is the internet. So i have unlimited data and minutes but my interet keep goin on and off i dnt have Wi-Fi so i use the data alot. Most of the times wen i use it a white circle would pop up where the 3g supposed to be and wen that happes my internet stops working the only time my internet do work is wen it say extended.

Maybe a slow connection

The circle means it's trying to find the internet but is unable to.
When 3G is there, that's when you're able to use it.