Slow internet connection

Slow internet connection. Paying for “Fast” plan which should be up to 600 Mbps.  Run an  Ookla speed test and only have 18 Mbps download.

Tried to use the Xfinity chat agent and it is useless. Doesn’t provide any support, says everything is “healthy” and good.  And points me to look at my equipment.  

posting here to get some real support.