I bought a jailbroke iphone 3gs 4.3/6.15 with new bootrom on it. I unlocked it using ultrasnow, no probs. However, when I went to put in my working tmobile sim card, no carrier comes up. It doesn't say Searching, it just doesn't say anything! I am not sure what to do since I know it is a tethered jailbreak. What i want to do if possible, is upgrade to 4.3.3 so it can be untethered jailbreak, rejailbreak it and re unlock it. Is that possible,and how do i do it, step by step. Thank you so much!!!