If the WiFi reception is still bad after changing channels on the router, then I suggest that you get the phone replaced.I've had my note 8 now since Friday and it is a nice phone for what I use it, couple of hiccups here and there but overall Im happy.
There is one thing though, the wifi signal is very bad on the phone. I am sitting in line of sight, about 8m away from the router and the signal is low.
On my previous phone (Mi 6) I could walk outside in the street and it would still be connected. Is there a way to fix this or see why its like this?
We have 2 Note 8 phones at home and they both have great WiFi reception.