def billing_address(params = {})
country_code = lookup_country_code(params.delete(:country))
add_field(mappings[:billing_address][:country], country_code)
add_field(mappings[:billing_address][:address], [params.delete(:address1), params.delete(:address2)].compact.join(' '))
province_code = params.delete(:state)
add_field(mappings[:billing_address][:state], province_code.blank? ? 'N/A' : province_code.upcase)
params.each do |k, v|
field = mappings[:billing_address][k]
add_field(field, v) unless field.nil?
end
end