My broadband cable speed has been very poor for months and I'm so fed, about to quit Optus and go with Kogan NBN. My family has taken to using 4G on mobiles in place of the awful broadband.
I get the feeling that since the HFC cable network is being shut down that Optus doesn't really bother with it any more. I can't even get through on the help lines. They are always "busy helping other customers". After 12 years, so long Optus!!
Without more information it's very difficult to say, but if you are already in an "NBN Ready" area, eventually Optus will want to disconnect their old HFC service anyway and run it all over the NBN.
Is it slow just during peak time or all the time?
What Optus modem are you using?
Have you restarted said modem? (I would do this by unplugging it for 5min which then forces the modem to completely re-register with the HFC Head end).
If this doesn't resolve the fault, can you login to your modem (http://192.168.1.1) and copy/paste all the cable RF stats into here?
If you are "bridging your modem" into another device, what is this device?
What if you remove this device and go straight to a PC/Laptop via an ethernet port, does the speed improve?
Thanks for the suggestions! I have tried most of them and with some temporary success. I even installed a timer on my modem to switch off power every night so that I get a fully reset modem each day. My setup is very simple, no bridging devices. I have had some good days recently and today I am able to make this posting so I am grateful for that, at least my broadband is today working. However, I conduct some of my business from home and my kids use the broadband so the many days of unreliability are very inconvenient. I saw recently that the NBN is now available in my area although it is quite a bit more expensive than my existing broadband, I have just signed up for the NBN100 plan on Vodafone. It can be cancelled anytime so I will see how it goes. In all this time, Optus could not even spare me a few minutes with a tech advisor so I am not sorry to see them go.