My experience using the call button last year on UA Aspen to Denver: I fractured my leg skiing and was in a hip to ankle splint and on crutches. I pre-boarded along with a couple of other passengers who needed extra time boarding. One elderly, very large, pre-boarding passenger on oxygen fell and landed on his back in the aisle. I couldn't get up having parked my crutches so i rang the call button. Zero response from the FA's. Other passengers helped the guy on oxygen up and in his seat.
The FA finally DID turn the call button off when we were approaching DEN.