'This function is called after the user selects a purchase type of "Business" and
is asked to enter the optional billing details. The billing details are updated
for that order.
company_name - Name of purchasing organization
company_contact_name - Name of the key contact at the company the sale was made to
company_contact_email - Email of the key contact at the company the sale was made to
recipient_name - Name of the company should the invoice be sent to
recipient_email - Email of the company should the invoice be sent to
customer_reference_number - purchase order number of the organization associated with this Order'

def add_billing_details(self, company_name='', company_contact_name='', company_contact_email='', recipient_name='', recipient_email='', customer_reference_number=''):

    self.company_name = company_name
    self.company_contact_name = company_contact_name
    self.company_contact_email = company_contact_email
    self.recipient_name = recipient_name
    self.recipient_email = recipient_email
    self.customer_reference_number = customer_reference_number
    self.save()
