Long story short, I got a replacement Air a few days ago and my replacement didn't come with a sim card. I had to go back to the Apple store and they gave me my old sim from my defective unit. I can log in through settings and see my data plan, but every time I try and browse the internet I am sent to a T-Mobile site saying that my pass has expired. From what the Apple website and a search in these forums show, replacement, or new iPad's should come with a sim card already in them and all you have to do is log in to activate your new iPad, thus deactivating your old sim. Is there an IMEI/iPad serial number confusion here since this thing should have come with a fresh SIM card? Thanks.