Speed test the service to a Router mode Hub(3/4/5) + your device with the link below.
Once the test begins click on: Run full test to see all the stats.
The speed at the Hub should reflect your subscription.
The speed any WiFi device draws data at is limited by its data needs and technical abilities.
Thanks for posting and sorry to hear you've been getting some slow speeds.
Can you confirm if it is just this one device you're having the problems with?
Have you rebooted the hub recently?