Walking into the shop and placing the bag on the counter, I said to the cashier, "I'd like to return this, please."
"Is there anything wrong with the item?" she asked.
"No, nothing," I replied. "It's hardly been used and I just no longer need it."
"Sir, this bag is empty," the cashier exclaimed.
"That's right," I said.
Spoiler:
"I'd like my

five pence."