Usually providers will charge depending on distance and network. This you can define here.
To create a new charge zone choose "New" from the action picker.
Enter the desired description for the charge zone and define the shortcut for it. Tap on "Save" to store the informations.
To remove a charge zone choose "Delete" from the action picker.
You can define one charge zone as the default. This one will be used as default when editing the providers.