3G doesn't connect but wifi does

[Robsmom10]

I have an IPad with 3G. I have a data plan with AT&T and use it to connect to the internet when I am not in a wifi zone. For the last two days, the 3G is unable to connect ...I get five bars in the indicator in the upper left hand portion of my screen, but radar-looking symbol does not appear to the right of the AT&T symbol in the left hand corner. When I view my account in the Data Connection screen, it shows that I have not used any of my monthly allotment.

Help! What do I need to do?