I haven’t heard of them, but if someone advertised unlimited internet and cut you off for 400GB of data then I think they would get in trouble for false advertising. If you average 400GB a month and occasionally hit 700 or 1TB I wouldn’t expect to have issues.
I often hit 5TB+ and never even considered I might hit a fair use policy. 1TB or less is well within the “I just watch a lot of Netflix” defence and so I wouldn’t be too worried about it.