Wirelessly posted (7250: BlackBerry7250/4.1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/109)
You need to update the software on your device to 4.1. Refer to Mark's FAQ at the top of the forum for details on where to download.
Once you have 4.1, on Bell you'll need to visit a Bell store to have the latest PRL installed. Your device won't connect to the EVDO network without the correct PRL. The store also installs a mobility update which enables modem tethering.