This link may be of interest to you.
The following quotes taken from within the above link may be of help to you.
As I'm in the UK and without LTE anyway, I've switched the phone to WCDMA (UMTS) mode only, which has helped though the phone now just flips between HSPA and HSPA+ when in poor signal. Its certainly much more usable this way at least.
This phone is packaged with very thin plastic wrapping over the metal band that runs around the circumference of the device. I accidentally left a lot of this wrapping on for the first few days. It may be complete crap, but I think my signal might have improved since I removed it all! I certainly seem to be able to maintain a connection in places that I wasn't able to last week, and maintain a constant (4-5Mbps) HSPA+ link in areas that I couldn't before..
The general concensus seems to be that the phone has poor reception.
You may also like to see if there are any system updates applicable to your phone. Scroll to Update Software in this link to find out how to do it.