Sorry to hear you're having some issues with the Optus Network in the Sydney CBD. I had a look into that location and I'm unable to see any reported outages.
Are you currently on a a high level of a building and experiencing network issues? Sometimes the higher up you are in a building, you will notice some network issues as the towers and boosters may be some distance from you. It may also have to do on how the building was built as it could interfere with the signals.
You can also try turning on Voice over LTE (VoLTE) and WiFI calling if you have a compatible device from Optus, this may help with any call issues. With these turned on, calls will be picked up through the internet to carry the call. To do that, follow these easy steps on our WiFi calling support page.
If you’re still needing a hand, we recommend messaging us via the My Optus App. The team is available 24/7 and are ready to assist customers as quickly as possible.