I recently switched to the TMobile plan and got the $25 data plan ( I wanted a 9.99 plan but the damned guy scanned my N95 IMIE and siad I had to take a smartphone plan).

But even with the $25 data plan the network positioning does not work for me.
I left it on for around 7-10mins indoors - and it still does not work for me.

Data is always on and works fine. But I am thinking I will downgrade to the 9.99 plan and see how it works.