M&S Lightweight Luggage Incorrect Descriptions

Our cases were damaged on a long-haul flight so we decided to buy a strong but light case. On the website, the M&S Longhaul Astrolite Rollercase (Medium) looked just the right size & they had them with 20% off so we ordered one on-line. When it arrived the capacity & dimensions were not at all as advertised. We then saw a review from someone who had a similar complaint who also found the larger size was incorrectly described too. What annoyed us was the uninterested attitude of M&S customer services when we phoned. Fortunately, the local store was much more helpful & will replace it with the larger case & take off the 20% reduction we would have had on the smaller one. The larger case is actually close to the size advertised for the medium one. The case is ultra-light with a reinforced base & much cheaper than well-known luggage brands so I hope it proves to be good.