What type of service are you running?
What did Optus say when you contacted them? If it's their product I'm surprised they can't help getting it to work. More details would help
Sounds like there might be a fault in your area. I would call them again though because it sounds like you don't have the whole story and you might have just got someone who wasn't well experienced.
Ideally you want to know what the cause is, what the fix is, who will fix it (you, Optus or NBN) and how long it will take.