Casio — Edifice watch exchange

I have purchased edifice watch for Rs 8295 from Casio showroom in Trillium mall Nagpur. While purchasing I said that I can exchange the watch if my brother doesn't like it. He said that in 1 month you can return anytime. But today when we went to exchange it he said that he never said 1 month. He said 1 week. How can people deny from saying what they have promised. Such a pathetic experience.