Exchanging an item on sale

 I’m a client of a certain bank. There was a discount for the clients of this bank at a disposable dishes store, “buy 400 NIS’ worth, and pay just 60 NIS.” But the discount applies only to a certain brand, that was sold in this store. I need a product of a different brand. Am I allowed to buy the brand that’s on sale, while taking advantage of this discount, and then to exchange what I bought for the items that I actually need, that cost the same amount of money?

It is forbidden to buy an item on sale in order to exchange it. You are only allowed to exchange something if you originally bought it in order to use, and then decided to exchange it.