Its a bit unclear what has happened. Why do you believe you can't recharge online? Does something come up to say you are blocked?
As a short term solution I would suggest just (completely separate from Optus) and order a Boost Mobile $150 which gives you 80Gb for 12 months (or $12.50 a month). You can either port your prepaid number across or just have it as a second SIM to put in your phone. It will be delivered to your door.
Otherwise Optus have prioritised your situation. It may take a wait or several goes (but its not like there's much else to do in isolation) but phone through:
Faster (Perhaps): Dial 133 937. Mon - Fri: 8am - 7pm (AEDT) Sat: 9am - 5pm (AEDT)
Perhaps don't press 1 and hold the line, you'll either be on hold and get through to someone or get the standard IVR to enter your service number and follow the prompts and press 3 to cancel. Times can vary from a few minutes to many hours.
Alternatively: Leave a message in the Optus Mobile App (If possible) or try Optus Twitter or Facebook sites.
On the plus side, after two weeks you'll be on the other side of this and able to walk around without a concern.