My problem with OPTUS started two months ago.
My website cmca.org.au is not accessable by all Optus network (landline or mobile). It is not blocked by Optus, but they just can't fixed it due to their bad DNS problem. I know changing DNS server of my PC to 18.104.22.168 and 22.214.171.124 (google) will solve the problem, but it still don't allow my mobile to access my site. Not to mention all the users out there who is using OPTUS network, they can't access my website too.
I can't imagine a company of the scale of OPTUS is unable to get their house in order. TIO or whoever is regulating the Industry should ask them to show cause or penalise them for their incompetance to operate the network. I am sure I am not the only one out there who had the same problem. I hope we can share our views here.
the site ever hosted by Optus? If you've moved the domain elsewhere, there's nothing automated at your old webhost to remove the DNS entries unless you ask to have it done (unlike say porting a mobile). If Optus still think they are the host, their DNS will be probably be pointing visitors to their old hosting space.