Most of the genuine stores (both physical and online) would have some kind of return or exchange policies. Read the policies before ordering. Usually you can return merchandise within 15 to 30 days of your invoice. Note: The countdown clock starts from the invoice date (when you ordered), and not when it was shipped or received. So you may actually have a limited period to time to test and return the item if it doesn’t come up to your expectations, or you find something defective.
The claim for missing or transit damaged items has a very short timeline (sometimes a couple of days).
Does not just ship back the item expecting to get a refund. Before you pack and ship, usually you need to obtain a RMA (Return Merchandise Authorization) either online or over the phone. Without this RMA, your merchandise won’t be eligible for return or exchange.
Also, while returning items, you need to make sure that you have included all the accessories and manuals that came with the original item. Must also be shipped back in the original box (not the delivery box, though that helps when trying to get the right shaped packaging box). I usually keep all packaging for a couple of weeks before discarding them.
For a nominal amount some of the stores will let you create a FedEx or UPS shipping label when you get your RMA. I find this convenient as the label has the correct return address, bar code and a tracking number. It actually is cheaper than trying to ship it yourself.
Always print two copies of the RMA / Shipping label. Stick one on the top of the package, and keep the other one inside the package. Just drop it off at the nearest courier store, or you can get the package picked up from your address. Give a few days after it reaches the store to get an acknowledgement from them, and maybe a week to get your refund.