It can happen to you on the Samsung Galaxy S5 that incoming calls are automatically answered when your headset is plugged in. This is especially annoying if you are just not able to call or if you do not want to speak to the caller for any other reason. The automatic answer of incomings calls when your headset is plugged in, is a function within the Android OS, which is usually not activated. However, this feature can be very useful if you are traveling by car.
Would you like to disable the automatic call answer, then you will find the appropriate option in the sub-menu of the Android settings. To change the setting, proceed as follows:
Open from the home screen the menu and then the settings. Scroll all the way down to the section "Applications". There you can tap on the button "Call". In the next menu tap on "Call Accessories". Here you will see at the beginning the option "Automatic answering". Remove the tick in the checkbox to disable this function while a headset is connected to the Samsung Galaxy S5.
Immediately calls are not automatically accepted by your Samsung Galaxy S5, if you have this connected to a headset.