Ok so I have an ATT account and an iPhone 4. No knowledge of the SIM card slots on current iPad so I am wondering. Can I remove the SIM from my iPhone4, pop it into the iPad and use it without issues from ATT? Seems I never use the iPhone for voice calls anymore, just email / browsing and my eyes would love a larger screen. I have a 'grandfathered " Unlimited Data " plan so do want to go to ATT to have this done and risk losing that plan at the moment.