Phone Networks determine how a Digium Phone should behave, depending on the IP address and netmask of the Phone as it sits on the network. If the Phone cannot get on the network because it is trying to use the wrong Phone Networks information, use the Phone's Select Network option to select the Phone Network that matches the network you want the phone to use. This is accessed via the Phone’s Main Menu > Preferences > Select Network.
For more details, see the Switchvox Admin Reference Manual.