So in the Past line A (Mine) has not been able to be upgraded so i used line B (my fathers). That was done for my 3GS. Now the iphone 4 is out, line A is able to be upgraded (which is happening), but line B is not. that is the problem heres my ideas. Line C, or D (mother/sisters) line is upgraded and swapped out for line B. Issues is, C or D will be using iphone 3G's and will not support the new microsim, and the old SIM from line B wont fit into the iphone 4. Solution( which i need your ideas on). Do the whole setup, upgrade the "wrong line" C, go to an ATT store, say they (C) have decided to go back to the old phone and are giving the new iphone 4 to line B, and we need new SIM cards activated. Is this doable ?