I need help understanding yes and no statements

Question

I am just getting started with python, and am trying to build a simple project to further understand yes and no questions.

In the following code, after displaying the second question and a user inputs yes - I get no return. What am I missing in this very simple code?

print ("Hello And welcome to Jims Grab and Go")
user_input = input("what is your name? \n\n")
print ("Hello " + user_input)

user_input = input("May i interest you in our world famous chili dogs?\n\n")

def yes_or_no():
    while True:
        answer =  input("Yes or No?").lower()

        if answer == "yes":
            print ("""Sure thing, I'll get that made for you, your total will be $5.50""")

        elif answer == "no":
            print("well then, what can i get for you today?")