app/helpers/billings_helper.rb
module BillingsHelper
def chargify_signup_link(text, product_id, options = {})
options.reverse_merge!({
reference: @account.id,
email: current_user.email,
organization: @account.name
})
link_to text, "https://#{Chargify.subdomain}.chargify.com/h/#{product_id}/subscriptions/new?#{options.to_query}"
end
end