“You previously logged in to”

Facebooked or the iphone OS is forcing me to login to my Instagram, Tinder, etc...with another account. I keep getting a page which says “You previously logged in to” Instagram, Tinder, or whatever “with facebook”. “Would you like to continue?” In the past I was given an option to login with another account. Or I could simply logout of my Facebook app or Safari Facebook login and that would fix the problem. How can I switch between accounts? An aquaintance used my phone and really I need to get back to collecting more wives online:P