@williamtan Yes Crowd is a public forum and not a direct support point for Optus.
You may be just in a bad spot or the construction material used in the building maybe an issue.
Where I live Optus is good and Telstra not so good.
Please message Optus Support 24/7 from the My Optus app. If you do not have access to the My Optus app you can use social media to contact Optus Support, please send a PM to Optus on Facebook or a DM on Twitter and include in the message you do not have access to the My Optus app.