I just did this for Rogers and it worked. No more EDGE. I tested it by turning off wifi and trying weather, stocks and safari. It won't connect with EDGE anymore.
Copied the instructions below another forum, with some changes for accuracy. As stated earlier, make sure you have SSH installed from Cydia and you can use an SFTP program (I used Cyberduck) to connect to the iPhone.
1) Activate open SSH and connect to your iPhone
2) Go to /system/library/Carrier Bundles/*your Carrier*.bundle/
3) download carrier.plist to your Desktop and rename it to oldcarrier.plist (just for backup)
4) download the file again and open it with "Property List Editor" (part of the Developer Tools. Get it from your OSX Install DVD)
5) Click "File->Save as" and save it as "XML Property List File" to your Desktop
6) Open the file with TextEdit
7) Add the following lines:
Code:
<key>AllowEDGEEditing</key>
<true/>
just below
Code:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
at the top of the plist file.
8) Save it
9) Upload and replace the modified carrier.plist to the directory, from where we got it.
10) Restart your iPhone
Go to Settings->General->Network->Cellular Data Network on your iPhone. You'll see the APN settings. Tap APN and the keyboard pops up. I simply deleted the APN line (made in blank).
... and your done!