code: public Subscription changeOfferChangeCaptureDateAndRefund( String subscription, Offer offer ) {
      return changeOfferChangeCaptureDateAndRefund( new Subscription( subscription ), offer );
    }
docs: Change the offer of a subscription.<br>
  <br>
  The plan will be changed immediately. The next_capture_at will change to the current date (immediately). A refund
  will be given if due.<br>
  If the new amount is higher than the old one, a pro-rata charge will occur. The next charge date is immediate i.e.
  the current date. If the new amount is less then the old one, a pro-rata refund will occur. The next charge date
  is immediate i.e. the current date.<br>
  <strong>IMPORTANT</strong><br>
  Permitted up only until one day (24 hours) before the next charge date.<br>
  
  @param subscription the subscription
  @param offer the new offer
  @return the updated subscription