I used a sim to call and text only when I saw my friends using the Iphone with a sim cut. I also buy an iPhone4s(AT&T) and put my sim cut in the Iphone. I use it more than 2 months without any charging, but until yesterday when I saw a 4G thing on my iphone and I try to use the internet, and I can go to facebook, download apps from appstore… I share a line with my aunt, so I called her and asked, Did she turn activate my sim to use the data. She said, no. Then she check her att account, and she saw they charge $30 more in my line, but last 2 month, there are nothing charging. She called to AT&T and asked why. They said, my Iphone have a feature that can activate the sim to using data when I put my sim cut in. I just have a question why, If it's automatically, it definitely activate 2 months ago, not using more than 2 months and it's automatically turn it on.
Some people just told me if you unlocked your Iphone, so the AT&T won't know that you're using the iphone and won't add data in your sim.
I just want to make sure IS this right? Or Are there any other ways to use the iphone(AT&T) without data plans?
Sorry for a lot of error grammar because I just came to US almost 1 year.