Does Apple take back a iPhone 6 plus if you used it for a week?

So i bought my iPhone 6 Plus last week, but i kinda regret getting a phone this big, and i want to get the smaller one now. I heard Apple takes back products within 14 days, but is this also the case when you have used your phone for a week? It is still in a perfect state though.

I bought a case for my iphone 6 Plus from http://pickyourkicks.tk

I'm guessing their would be some cost involved as its now a used phone.

Yes just bring the receipt!