I need help with the MasterTIcket (Try, Exception) I got stuck with a NameError

TICKET_PRICE = 10

tickets_remaining = 100  

service_charge = 2

def calculate_price(number_of_tickets):
    return number_of_tickets * TICKET_PRICE + service_charge

while tickets_remaining >= 1:
    print("There are {} tickets remaining.".format(tickets_remaining))
    name = input("What is your name?  ")

    try:
        number_of_tickets = int(input("Hello!, {} How many tickets would you like?".format(name)))
        if number_of_tickets > tickets_remaining:
            raise ValueError("There are only {} tickets remaining".format(tickets_remaining))
    except ValueError as err:
        print("Oh No! That's not a valid value. {}. Please try again".format(err))

    else:
        total_price = calculate_price(number_of_tickets)
        print("The total price is, ${}".format(total_price))
        proceed = input("Are you sure you want to proceed with the purchase?\n Y/N?")
    if proceed.lower() == "y":
      print("SOLD!")
      tickets_remaining -= number_of_tickets

    else:
      print("Thank you anyway, {}!".format(name))
print("Tickets are all sold out.")