There are other wireless networks within range, but i have never connected to any of them. How do i order the networks by priority?

And i doubt that i am out of range. The router is sitting on the desk three feet from the phone. I can connect through UMA, and go into the other rooms and talk just fine when i turn the tmobile network off, so i know the range is pretty decent, it just switches to the tmobile network instead of using it.