Failed to sign in to Facebook notification message won't stop ringing. How can I get it to stop?

[AC Question]

Failed to sign in to Facebook notification message won't stop ringing.

I keep getting a special ringtone message that my FB sign in failed, but I am already logged in and the notifications are coming every 15 minutes. Has its own sound and I can't turn it off. Now am not getting a ringtone notification of text messages. Time for a new phone? iPhone will be next!