How do I file a complaint against UPI?

You can file a UPI complaint through the UPI app you used for the transaction, your Payment Service Provider (PSP) bank, or directly on the NPCI Dispute Redressal Portal. NPCI, the central authority for UPI, manages a tiered system for resolution, involving the app and banks before final review. The official NPCI UPI complaint number is 1800-120-1740.