Sony’s new PlayStation Store refund policy allows for refunds within 14 days

Full games, and add-ons (DLC) can be refunded within 14 days of purchase, but only if you didn’t start the download, install or stream process. If the content is “faulty”, you may be granted a refund after downloading or installing it.
The new refund policy can be seen on the North American support site, the UK site as well as those for other regions.