Your return instructions would either be on the receipt or you could have asked at the time of your purchase.
Check with the store so you know what you're getting into before you purchase something from them.
Aside from that, you do have a warranty with SONY. It may be frustrating when a product has issues, but the store is not responsible for the quality of a product--the manufacturer is!
Since you can't typically purchase these items directly from the manufacturer, the stores are only helping to provide products that customers desire.
This is another typical case of a misinformed consumer who will take down the closest person or entity within reach when something goes wrong, instead of going after the company who made the product in the first place.
I deal with this issue all the time as I work for an extended warranty company.
Since taking this job, I have learned so much about my responsibilities as a consumer and it has gotten me a lot further with manfuacturers when I'm having customer service-related issues.