Wirelessly posted (Cingular 8100 Pearl: BlackBerry8100/4.2.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)
Even if it did work, TMO's $19.99 pricing is only available if you're on their $29.99 voice plan.
So hypothetically, you'd have a $29.99 Cingular voice + $49.98 TMO. I guess you're saving money sticking with one carrier.
Sure would be nice to pick and choose components of service though.
9630 Tour - Sprint