Share your experience!
i used my WT19i more then 14 months. last 15 days i m getting serious network problem. when i were on the rode side i got full network but when i enter home/shop/market there is no network. i installed the latest update 4.0.4 no result. again i installed old update of 4.0.4 again got no result ... is there any solution? 
Have you tried another SIM-card/ network provider to see if there is any difference?
Have you tried to do a repair of the phone software?
Click on this link to get Sony PC companion:
http://www.sonymobile.com/gb/tools/pc-companion/
Start PC companion, start "Support Zone", start "Update phone software" and click on "Repair".
Follow the on-screen instructions.