title: Set custom shipping rates programmatically in Woocommerce 3
body: <p>I have searched and found a number of examples of how to change the shipping rates. Basically I am looking to do the same, but I want to use a 3rd party API.</p>
  
  <p>I have set up a custom plugin with a functions.php and activated it.  I think used something simple like this:</p>
  
  <pre><code>add_filter('woocommerce_package_rates','test_overwrite',10,2);
  function test_overwrite($rates,$package) {
  
      echo "&lt;h2&gt;Can you see me&lt;/h2&gt;";
      foreach ($rates as $rate) {
          //Set the price
          $rate-&gt;cost = 1000;
          //Set the TAX
          $rate-&gt;taxes[1] = 1000 * 0.2;
      }
      return $rates;
  }
  </code></pre>
  
  <p>However when I run either the checkout, or basket, the filter does not seem to run because I cannot see the <code>echo</code>.  I also tried <code>print_r()</code>. </p>
  
  <p>Am I missing something as to why I cannot run this filter ?</p>