Returning merchandise is normal in many western countries as a protection of consumer right. Use below english conversation, if you feel that the products you buy are not as you expected as the first time.
Example 1
You : I'd like to return this CD player.
Seller : Is there something wrong with it?
You : It's not compatible with my stereo system.
Seller : Can I have a receipt?
You : Here you go.
Example 2
You : Can I return this CD player?
Seller : Sorry. We don't have the policy to accept any returning merchandise.
Example 3
You
: Can I exchange this CD player for something else?
Seller : What's wrong with it?
You : I don't know. It doesn't work well to me.
Seller : You' ve got the receipt with you?
You : Yes. Here