How do I get my phone to connect to WIFI automatically if available?

[AC Question]

I turned wifi on but it keeps turning off. I'm using to much data. Can I set it to default to wifi if available?

 

[Sam_Gs7]

If you want quick replies. Please report what phone brand is that.?
To quickly find if your phone has this setting, consult your Phone

User's manual..Mention that 'cause I switched from SGs5 to Gs7
and can't find the Auto..option when I turn On Wi-Fi: But tap
on "More" and check what options offers. Post results