How to loose a customer, save a few quid and waste a lot of every bodies time
1) Sell them two packs of Morrisons own mushrooms that are well within their sell by date but turn out to be old bruised and inedible. Therefore wasting the customers time trying to cook them and ruining a planned meal.
2) Provide an online complaints form that has several time wasting flaws and don't ask for all the information you need.
3) Ask for the remaining information (a receipt) a few days later when it has been lost.
Ignore that the product was Morrisons own brand, that photographs were provided and that the visit used the Morrisons-more card, ignore the sale of goods act and instead repeatedly insist on the receipt according to your unreferenced T&C's. Tell the customer "please know that your comments are still being taken seriously".