In message , at 04:57:17 on Tue, 12 Sep
2017, Anna Noyd-Dryver remarked:

Of course there is always the option - possibly heresy for Millenials - to
switch off wifi on your phone. I know, its radical, but it might just work.

I usually forget to switch it back on and end up using my 4G allowance at
home...

My Android phone uses wifi in preference to mobile data, when wifi is
available.
--
Roland Perry