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Did you test the speed via WiFi or Wired connection?
If via WiFi, are you connected to the 2.4GHz or 5GHz band network?
You may also check this article that will guide you on how to troubleshoot a slow speed issue.
Please send me a PM with your TPG username or customer ID number if you need further assistance.
I received the PM and understand that this case has been raised to our Engineering team.
They are currently investigating the issue as the modem/router is receiving the correct upload speed for your NBN plan.
Your assigned Engineer will be in touch as soon as an update becomes available.