Yes, it is a SIM for smartphone because I was in the AT&T store and showed them my phone before I bought anything.. and I do get data to work.. But sometimes it keeps revolving on the type of data. Other times it will lock and work just fine. That's what my problem is.
Glad the guy at T-mobile knew what he was talking about.
Samsung Galaxy SII I9100 mobile from Vodafone (UK Edition) running on the AT&T network in the USA
Currently running NeatRom Lite 4.3 & Jeboo 2.1+ kerenel
Samsung Galaxy Tab 10.1 WiFi only (USA Edition)
*retired* Rooted Motorola Droid X on Verizon