Where to complain if UPI is not working?

You can first register a complaint with your UPI service provider's customer support, which can usually be found on their official website or within the UPI app. For example, if you use a payment service like Paytm, you can use the built-in support feature. If the issue is unresolved, you can report it to the National Payments Corporation of India (NPCI) through their official grievance portals or helplines.