Question

Scenario:

Anna, a young entrepreneur, owns a successful online retail business that specializes in handmade crafts and accessories. She recently launched a new product line of eco-friendly bags made from recycled materials. One day, Anna received an order from a customer named Carlos, who purchased one of her eco-friendly bags for Php 1,000.

A few weeks later, Anna discovered that Carlos had mistakenly been charged twice for the same bag due to a technical glitch in her online payment system. As a result, Carlos was charged a total of Php 2,000 for the bag. Anna realized the error and immediately contacted Carlos to inform him about the double charge and apologize for the inconvenience.

Carlos, after reviewing his bank statement, acknowledged the double charge and expressed his desire to receive a refund for the extra Php 1,000. However, Anna, who had already shipped the bag to Carlos, informed him that she was unable to provide a refund at the moment due to financial constraints.

Carlos, disappointed with the situation, seeks legal advice. He believes that Anna's failure to refund the extra Php 1,000 constitutes unjust enrichment. He argues that Anna should not profit from the inadvertent overcharge, and thus, has a legal obligation to return the excess payment.

Question:

Based on the scenario, analyze whether Carlos has a valid claim for unjust enrichment against Anna. Discuss the pertinent provisions of the Civil Code (Arts. 22-23 and 2142-2143) and explain the necessary elements to establish a claim for unjust enrichment. Apply these elements to the scenario and state your legal opinion on Carlos' claim.