Turning off billion wireless router loses settings

Your router may have an issue, unless you are resetting it rather than just shutting it off. Check to make sure the procedure you are using to turn it off is not a "reset".

If you are just powering it down, and it's not keeping it's settings, you may need to replace it.

I suspect you need to press the reset and then re-enter all the settings.

When you have done that make sure you save before exiting and (if indicated) actually formally log out of the router setup screens (don't just close your browser).