Disgruntled customer

Game retail (online) ran a promotion yesterday on Bakers Romany creams 1kg . Having placed my order yesterday and payment was successfully made, I received a mail this morning cancelling my order with no explanation provided. Upon calling them the reason given was that they do not have stock and the online promotion is still visible. This is totally unacceptable business practice and would like Game to fulfill my order or provide me with a rain check so that i can get the item when stock is available.