Try these two things....
First one, be in an area where you know that wifi doesn't exist. Then go into wifi settings and do a manual search. It might reset the list for you.
The second thing to try is..... Go into your app manager under all apps....
Find every app related to IP, wireless, and wifi. Go into them and clear out the cache in each app.
That's the best I can recommend short of doing a factory reset.