You may check this article out:
If you have a bundled service with us and uses the VoIP phone, then we recommend ordering a new modem/router from us.
The VoIP service will not work with any of the third party devices.
Hi @reynaldog . TPG should be offering to run a line test in case low speed is caused by fault in the NBN network. You might ask for this.
What type of NBN connection do you have?
Have you run the speed test on TPG support page?
Is slowdown occurring on ethernet computer and/or wifi devices?
If wifi, it could be wifi interference.