Facebook Messenger Video Chat Ringtone

How do I change the ringtone for Messenger video chats? I don't like the one I have now because it is hard for me the here. There seems to be no way to change it under Notifications and Sounds. I do get a sound for when someone leaves me a message but is different than the ringtone for video chats. I am able to change the sound for a message. All the videos I watch about changing show a Ringtone option under Notifications and Sounds that I don't have.