I bought a Billion 7300N RE ADSL modem a couple of months ago from Matrix.
The wireless network keeps going down if not used for a couples of hours and it never comes back up. Only way to get it working again is if you reset the modem.
I see many people have the same problem with this modem http://forums.whirlpool.net.au/archive/978788. Also here http://forums.whirlpool.net.au/archive/1130708
Spoke to Billion SA about it, they have no solutions.
Going to have to go spend another R1,000 on a new ADSL modem, the Billion 7300 has ended my trust in Billion over the last 5 years as a producer of reliable ADSL hardware.