@HURIMOZ 

Did you upgrade your modem when you upgraded your service?  For example, a DOCSIS 2.0 cable modem has a downstream limit of 40 Mbit/s.  This would be a very old modem.  Also, is this for both wired and wireless connections?  Please provide modem model # or research it;s performance specs.  It may be the bottleneck.

Changing the direction of your router's antenna can make a difference to the WiFi and Internet speed!

  @pcuttle Hi this is a test with the AX6000 speed test mobile app as well as the PC interface.

See version below:

  @mackriss20 I do the test with ethernet cable J45 6a, not wifi.

  @HURIMOZ 

Try updating your firmware.  Looks like you have an older version.  Also, if you want, there is a beta version available in a pinned message to this forum.  I have the same router as you and I have been running the beta just fine.

Also, did you get an upgraded modem when you changed your internet plan?  Like I said, if the modem is really old, it may not be able to take advantage of the better plan.  My ISP did that to me.  They sold me a faster plan but did not provide a new modem that supported those speeds.

  @pcuttle I've been living away from my AX6000 and can only use the online firmware update. I tried to update the firmware by uploading the bin file but the system rejected it and told me I have to connect directly to the home network. I'm doing a port forwarding to dyndns as I have surveillance cameras at home.

I assume the modem provided by the ISP is new and their technician went to the house once to do some speed tests. They used their own router that they provided and got speeds close to the 500/100Mbps they advertise.