For customers experiencing any issues with their NBN service, we recommend the best thing to do first is check if there's an outage on the NBN network.
We have created this article that can guide you on How to Check for NBN Network Outage
If there are no known outages in your area, customers can proceed with the troubleshooting steps indicated on this link : https://www.tpg.com.au/support/nbn-fttn/problems_speed_nbn_fttn
An article is also available that will guide you in troubleshooting a Slow speed issue.
We understand that you are under the NBN12/1 speed tier with typical evening speed of 10.9 Mbps Download speed.
If you are using a WiFi connection, then signal interference may also cause a slow internet speed.
We've created some articles that will help you improve your home network.
Feel free to search Community for help with your issue, or contact us and we'd be glad to assist you.