[Cicatrize]

It's called a "Premium Data" charge.

http://blog.laptopmag.com/sprint-cla...arge-on-evo-4g

If you buy the Sprint 4G EVO, you have to pay this $10 charge each month. This is specific to the device. It’s not related to whether you are using 3G or 4G. It is required if you have the phone.

Because the phone has a faster processor, a huge 4.3 inch screen and an 8 megapixel camcorder/camera, we expect you will be using a lot more data than you would with our other devices. These features will give you capabilities that have previously never been available on a wireless device and we think they provide a premium experience.