comparison of a replacement iPhone 4

I had a 16 GB in the box( MC608LL/A, part number) Model A1332, carrier No. 68094 IMEI 012544009770044, ICCID 89014103243737814209 826-9578A Had to send to Apple Care it was using data but nothing was running to use the data .It used 2GB in a wireless enviroment 95% of the time it was on. This was in 7 days. They sent me a new phone but it says model A1332, EMC 308B, FCC ID -BCG-E2380B IC 579C-E2380B I looked up the MHZ on both and they were different. What does that mean? Why did my first Iphone have an A where this was has a B ? This second one does not seem to find a signal like the first one did? Plus It had a full charge when I went to bed at *pm it is 3 am and it has 2% left on it?