Someone on OLX wants me to refund extra money — is that normal?

No — this is one of India's most common marketplace scams. Use OLX & Marketplace Buyer tool. A buyer 'accidentally' sends extra via UPI, asks you to refund the difference, then reverses or disputes the original payment — you lose both the goods and the refund. Never refund 'overpayments' outside the platform's official flow. Insist on in-person cash or platform escrow only.