First of all for an accurate speed test I would disconnect any 3rd party routers and run a speed check directly off an Ethernet lead from your Superhub 3 and run the speed check on either Speedtest.net or Fast.com.
If the speeds are still slow then give the modem a full pin reset which should fix any speed related issues!
( I am a Virgin Technician working from home so please consider giving me some Kudos if you feel as though this was useful ).
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