Hi there,
Telstra are currently pushing new firmware to all Techniclor Telstra routers. This is due to the firmware they pushed out a few days ago being buggy which may be the reason your ADSL connection isn't stable.
I please keep your router on for the next 12-24 hrs as Telstra may be trying to push an update through to your router. Once this period of time has passed, please manually restart your router by simply cycling the power.
I would imagine that you have been on the phone with Telstra and it took quite a while, so thats why Telstra has online livechat.
You are able to talk to a Telstra consultant online here: www.livechat.telstra.com
Hope I was of help!