I will call out (and often have*) VM when they mess up, but before accusing them of false advertising, can we have a bit more info on what's going on? Things like how you're measuring speed, what equipment this is on, whether you have looked at and can post** your hub's status data for the Downstream, Upstream, and Network log? This is a "community" forum, with input from available amateurs like me, and from VM staff, but it isn't an instant response chat service. Work with us, we'll work with you.
* I'm rather proud of my caution, telling me to reign it in or risk expulsion from the VM Forum, although that was a long while back and I was a big bit mouthy at that time.
** Select, copy and paste as formatted text. Screenshots cause nothing but problems.
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It is checking the speed through the Hub, that is why you need a device and cable that is suitable for the speed coming in.
If you are on 500Mbs and only getting 80Mbs it would indicate a problem with the device or the cable not being up to the job or a supply problem.
If you are on 500Mbs and only getting 300Mbs it would point to a a supply problem and that would require further investigation.
On Wi-Fi and a 500Mbs contract but only getting 20Mbs is it a wall, a week signal, interference from another wireless transmission. Nobody knows what is causing it, that is why speeds are measured at (though) the Hub