Getting an Iphone 4 from AT&T?

I want to get an iPhone from at&t and I'm planning on getting the one that's free with a two year plan, however I'm confused on the data and services for smartphone because it makes me pick. I'm getting it online, fyi. I don't know why i have to choose anything for the data and services for smartphones. If someone would explain that to me it would help a lot. I chose the $20 one and monthly i have to pay $90, can i maybe remove the data and services for smartphones and pay less?

They don't let you remove the data plan, with any "smart phone" you are forced into a data plan

Mhm, on AT&T data plans are required for all smart phones.