get '/account/plans', to: 'accounts#plans'
  post '/account/change_plan', to: 'accounts#change_plan'

#accounts_controller.rb
  def change_plan
    @plan = Plan.find(params[:plan])
    current_user.plan = @plan
    current_user.save
    render 'payment_options'
  end

<div class="plan-details">
    <header class= <%= plan.css %> >
      <h3><%= plan.name %></h3>
      <small><%= plan.visibility %></small>
      <p><%= plan.card_description.html_safe %></p>
      <span class="plan-price"><sup>$</sup><%= plan.amount.to_s %></span>
    </header>
    <article>
     <%= plan.features_description.html_safe %>
      <%= link_to button_text,  account_change_plan_path, title: button_text, :class=>"btn btn-md btn-block btn-outline-green" %>
    </article>
 </div><!-- end plan details -->

No route matches [GET] "/account/change_plan"