Data usage

[LegalAmerican]

I have 4 gigs of Data to use per month, and usually I am at about 3.2 gigs at the end of a cycle. Well on the 27th of this month I got the text from Verizon alerting me that I had used half my allowance (2 Gig). Well then on the 29th, my phone went from showing 2 gigs used to 3.128. I found this odd because I worked a 10 hr shift on the 28th where I RARELY use my phone.

Is there an app I can download to see an itemized breakdown of what my data is being used for? It's very odd for my phone to jump a full gig on data used in less than 48 hrs.