I would like to change this for a different size.
Example: "I would like to change this shirt for another size. This one is a little too small for me. Is that possible?" Answer: "Yes, of course it is possible. Please just take a new one."
Example: "I would like to change this shirt for another size. This one is a little too small for me. Is that possible?" Answer: "Yes, of course it is possible. Please just take a new one."