Your modem disconnects unexpectedly You may have call waiting turned on. If a call comes through with call waiting enabled, your modem will usually drop the connection. If Telstra resets their exchange the call waiting might be enabled automatically. Please check for call waiting from time to time or if you have problems with drop-outs. Telephone double adaptors and very long extension cables can cause drop-outs.
Phone cables come in different qualities.
If you are getting poor performance from the modem and a lot of drop-outs, good quality phone cable is worth investing in. If possible, try plugging the modem directly into the phone line with no other devices attached anywhere in the house. Try it, it might make a difference. If you have a digital mobile phone, telephony between such a phone and a GSM cellular base station can cause severe data transmission loss that can terminate a modem call. If you have a burglar alarm which automatically dials and transmits data, this will affect your line quality.