title: Woocommerce subscription plugin, downgrade or upgrade function
body: <p>I'm struggling now for a couple of days and can't find a good documentation or examples across the internet. I have the following situation:</p>
  
  <p>Users can switch their subscription for next week.
  They can choose how many meals they want based on the subscription of a variable product. 
  So one product contains more variantion products based on the woocommerce subscription plugin.</p>
  
  <p>So they can choose from 1 to 14 meals a week. The change they make on the subscription has to start the week after they made change on the subscription .</p>
  
  <p>What is the best way to update the users subscription. I can't find the right function for this. 
  I hope somebody can give me a push in the right direction :).</p>
  
  <p>I found a way to remove the order and replace this with the new one but i think it's not the right way.</p>
  
  <pre><code>    subscription = wcs_get_subscription($subid);
      $subscription-&gt;remove_order_items('line_item');
      $productnew = wc_get_product($id);
      $subscription-&gt;add_product($productnew,'1', $args);
  </code></pre>