Okay, mine is week 28 (the 4th and 5th numbers of the serial number), and 3G is crap. We continually put the phone in 2G mode.
Where do I find the Model number?
ps. Is it just a matter of going to an Apple store to replace?
grega the model number can be found in settings/general/about. near the serial number.
i have a week 27 489x on optus. i have also had a new sim, no help. i also tried the new sim in a model 500x (from memory) at my store of purchase, didn't help either.
edit - i have heard that people can 1-1 exchange at apple sydney, but they are charged a $40 restocking fee. you might like to call apple and confirm/deny this first.