Had our first negative interaction with Exetel's support today. :(
Shortly after about 3pm our connection dropped entirely, and when I checked things out the PPPoA was failing. I rang their support line, and got told that our modem had apparently reset to it's factory settings and they'd email me the settings I needed - I suspected that maybe this was because I was using PPPoA and they prefer PPPoE (though PPPoA has been working fine for us since the start). When I checked the details though, other than the different PPP method, everything was the same and it still didn't work.
Rang back again, and they said that there was probably something wrong with the line, and do I have dialtone. I don't even have a phone, how can I check for dial tone? Regardless, I have ADSL sync, and I've never heard of a situation where the ADSL syncs but the PPPoE failed and dialtone had any indication at all. All our numbers (SNR, BER, etc) all looked pretty good, but I decided to try a different modem just to make sure the error wasn't our end.
I dug out the old Netcomm modem, configured it and had a go. It has a bit more verbose logging, which indicated that it was definitely trying to make a PPPoE connection but the other end wasn't responding. Really looked like the problem was their end, but support were no help.
Then about 30 minutes after it dropped, it came back up and a few days later there's still no explanation from Exetel as to what actually happened.