Optus is probably not the world's worst phone company. Some British company would probably beat them for that title. But they would be in the running.
Would you like to take over somebody else's phone number? If they are with Optus it is a cinch. You just sign up with some other company -- say Dodo -- and tell them that you want the number. Dodo will then simply ask for it and Optus will give it to them no questions asked. You would imagine that Optus would ask their customer if he wanted to lose his number or not -- but no siree!
Sound crazy? It is. But Optus have just done exactly that to me. They cancelled my number and gave it to Dodo -- even though my account was paid in advance and I have had it for ten years without giving them any problems with late payments
I of course protested and it was then that I was told that they perform no checks if another phone company asks for a particular number. It's obviously a cost-saving measure for them.
After I wrote to Paul O'Sullivan, their CEO, about the matter, they got my number back from Dodo but tell me that they are so hard worked that it will be another week before my account will actually be restored. Most people who ring me have my mobile number but otherwise it would be a read teeth-grinder to lose my landline for 3 weeks. It could happen to you. Change to another provider.
I have been battling with Optus since the year 1999. You can read some of the correspondence here