Hi, new iphone 5 user here too, I the first few days i had no issue with 3G. but last few days, it just turns off by itself, sometimes even Edge! and what i had to do was turn it off and on again. after that it is ok. So far in the past 5 days it has happened at least once a day.

Anybody also facing this issue?

if anyone still can't find the iphone5 model they want, you might wanna check out their new online store ( which just opened ) . You can order from there.