Whomever told you that is talking rubbish. My household regularly exceeds 1tb a month and has no problems with speed. Perhaps they got confused with their Business Wifi service which has a FUP at 1GB a day?
As for your problem if it kicks in at the same time every day it may well be contention, 4pm is about the time kids are home from school.
However what I would suggest you also do is check the power levels throughout the day if you can. I had a problem where my speed would drop at midday every day, declining until it would stop working altogether.
This coincided with the power levels dropping lower and lower until they got so low the connection dropped. It turned out a component in the network was failing and got fixed when it failed totally and brought the entire area down.
It's been a while since I checked them but from memory once you've logged into the Hub you can find the power levels under the router status section. Again from memory the ideal is power levels around 0, you'll most likely have figures + or - either side, so long as they're relatively low you're ok. It usually drops the connection if the power level exceeds + or - 12 in my experience.
It's also worth posting in the VM forums, it takes them a while but a UK based support agent should pick up your query and will be slightly more helpful than an overseas one.
Edited by Lithurge (Wed 14-Nov-18 11:42:04)