Guaranteed delivery date not honoured for in stock items

<p>I placed an order on the site for a product that was in stock with express delivery so that I get the product by the 12th of May. The order confirmation said "Your order is being processed and your guaranteed delivery date is Friday, 12 May 2017"</p> <p> </p> <p>I was then told by the contact centre that the item wouldn't be delivered on the 12th of May and there is now a lead time of 5-7 working days for the item.</p> <p> </p> <p>How can you guaranteed a delivery date and then not honour it.</p> <p> </p> <p>What a joke!!</p> <p> </p>