How to keep facebook contacts on android after signing out?

[confused composing]

I don't sync my FB contact with my phone contact, so I can't say anything about that.
But have you tried to merge & sync your contact to Google dashboard? See whether the FB contacts also merged over there.


As for your concern using your data while you're not on wifi and while you're log in on FB, as long as you turn off your mobile data connection in your mobile, you're not connected to internet, thus it does not use your data quota. And even if you turn on your mobile data, as long as you don't open your FB eventhough you're not log out from FB, it does not using your data quota.