Welcome to TPG Community!
We were able to locate your account using your community details and tested the NBN network.
We weren't able to detect any fault and have seen that the sync speed is within range. The current sync speed that your modem is getting from the NBN FTTN network are 37809.0 kbps Downstream and 17765.0 kbps Upstream (Actual Throughput). The sync rate for the FTTN is greatly affected by the quality and distance of the copper line from the node to your premises.
May we know where did you get the information about the 'current line rate'? Are you able to share a screenshot of this information?
The speed of 23Mbps, was it the result of the speed test via WiFi connection or Wired connection? The WiFi connection is prone to interference which may cause the slow speed result. Are you able to test the speed via Wired?