UPI stands for Unified Payment Interface.
This is a new initiative from the Govt. of India.
These payments are through a payment gateway put up by the government. The feature is still new in our country and we face a lot of problem with this.
The payment might come through, but in case if there is a refund that has to be done, these accounts are a problem.
The refund keeps getting failed continuously.
I would suggest you avoid using UPI for payment.