Fix for 3g issues with T-mobile

Guide for 3g lock fix.

Phone needs to be rooted.

go into terminal, su (You can download a terminal from the market)
mount -o rw,remount /dev/block/mtdblock3 /system
vi /system/build.prop
goto the end of the file
hit a (for append)
Add the two lines to the file
press escape (Ball + 1 depending on terminal client)
type :wq! ( : won't show up)
cat /system/build.prop to make sure your lines are in there and look correct.
save, exit, and reboot (reboot twice).

TMO US:
ro.ril.hsxpa=1
ro.ril.gprsclass=10

TMO EU:
ro.ril.hsxpa=2
ro.ril.gprsclass=12

You can check to see if the changes took by going to your phone status and seeing if your version changed. It should be 32.19.00.16u (or whatever version you are on) on settings 2 and 12 32.19.00.16h (or whatever version you are on) on settings 1 and 10 (this one clears things up for T-mo US)

Info on settings
ro.ril.hsxpa=0 - UMTS r99
ro.ril.hsxpa=1 - HSDPA
ro.ril.hsxpa=2 - HSDPA/HSUPA

GPRS Class----Max. data transfer speed
Class 2--------8 - 12 kbps upload / 16 - 24 kbps download
Class 4--------8 - 12 kbps upload / 24 - 36 kbps download
Class 6--------24 - 36 kbps upload / 24 - 36 kbps download
Class 8--------8 - 12 kbps upload / 32 - 40 kbps download
Class 10-------16 - 24 kbps upload / 32 - 48 kbps download
Class 12-------32 - 48 kbps upload / 32 - 48 kbps download

source