Getting error while initiating refund in test mode

[Gagan3130]

{
statusCode: 400,
error: {
code: 'BAD_REQUEST_ERROR',
description: 'invalid request sent',
metadata: {},
reason: 'NA',
source: 'NA',
step: 'NA'
}
}

This is the error I am getting. I have made sure the payment was captured for the paymentId also. I made 2 payment. One was made with card and other with upi and in both case I am getting the same error when trying to initiate the refund

const refund = await razorpay.payments.refund(paymentId, {
amount: refundAmount * 100,
notes: {
refundReason: "user cancelled the service",
},
receipt: "rec_1234",
});

this is refund initiation method i am using