You cannot use Siri when you are in the middle of a phone call,so you cannot use it to end the phone call.
Call Apple and make a feature request.
I have an iPhone SE and I cannot figure out how to hang up the telephone with Siri. I am disabled and if I call somebody and get an answering machine or they don't answer or whatever I need to be able to hang up the phone with Siri.
Thank you very much in advance.