How to lock your iphone 3g and 3gs to the 3G / UMTS network ONLY

This guide will help you to lock your iphone 3g and 3gs to the 3G / UMTS network ONLY. this will lock out the EDGE and gsm mode! please read the ENTIRE guide before doing this mod or you will brick your phone

Here is how to do this:

1. Jailbreak your phone

2. install SSH (the windows version is attached to this board, for MAC users use google. The default username is: root ,and default password is: alpine , for the ip adress use the SBSetting), then activate SSH on your iphone (via SBSettings app that can be found in Cydia)

3. login as root

4. go do /var/preferences/

5. open the file csidata

DO THIS MOD AT YOUR OWN RISK. YOU MAY DAMAGE YOUR PHONE!

Inside csidata you will find the following line: GsmRegistrationModel::fRatSelection=0x1

The following values apply: 0x0(EDGE ONLY), 0x1(EDGE+3G), 0x2(3G ONLY).

1. Change to the desired value (0x2 in our case to lock the phone to 3G only) and save the file

2. Reboot the phone. you are done.

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Alternatively you can use an app called gtxtedit from cydia and edit that csidata file.

Please note that if you use the 3G/EDGE toggle within the iPhone menu, BossPrefs or SBSettings, you will lose the setting you just made above as those toggles can only toggle between edge only and 3g/edge mix and will overwrite the ctidata file.

All my other installed applications are working just fine. Please note that this will not improve your reception, it will just make the iPhone work in UMTS only mode and will disable the phones ability to fall back to EDGE. Your iPhone will NOT fall back to GPRS, so make sure you are in a area with strong 3g signal, otherwise you will not receive calls or use internet when you have only 1 bar of 3g signal. Because you say goodbye to 2G already. My iPhone gets speed max down 1050k, up 330k. So it's not bad! It works for me very well and I hope it will work for you