Why is there a circle where the 3g symbol should be on my Iphone 4s?

I just activated an iphone 4s from virgin mobile and ever since I got it, it has had terrible 3g coverage, everything is slow and half the time won't even load and the 3g symbol shows up rarely for like a minute and I'm very frustrated with this because I paid full price for my iphone to have it not work at all in the way I want it to.also, I can text and call fine its the 3g network that is not working.

Circle means its not connected to 3g or Wi-Fi.
virgin mobile has horrible 3g speeds and coverage, not worth it.

You're not getting 3G on your phone. Virgin Mobile is horrible.