The way I learned it is: Any statement of intent, no matter in which form, is creating a contract that you are bound to abide.

You sound like you would argue that it obviously was not a contract but a joke because 'why would a company pay something without getting anything in return'. But that would not hold. Companies spend a lot on customer relationship management. So the customer here could safely assume that the companies 'return' was a happier - in this case: less angry - customer.