I have switched from NBN50 to NBN200 superfast, however, now I only get 50Mbps download speed.
I have tried resetting, and turning off/on the modem and router.
Could you please look into this?
Are you still getting 50Mbps?
If yes, please check the QoS or bandwidth control if it's enabled. Change the value if possible or disable it, then test the speed again.
Also, did you test the speed via WiFi or Wired?