google pay api integration

Question

I am creating a project where i am creating an recycler application, in react and python django rest framework and i am creating a wallet where all the sold items amount will be credited in users wallet and the user can transfer the wallet amount to his bank account.

the problem which i am getting in googlepay API is i am getting an option to transfer money from users account to merchant account and i want to transfer money from merchant account to users account.

the code is there in python django rest framework.

I tried to use the refund api but the api needs the transaction id which was initiated at the payment time, but it is not possible.

And now i am thinking a new approach to make user as a receiver and merchant as a payer using a post api of googlepay, and the json provided be as follows

{
  "merchantId": "MERCHANTUAT",
  "merchantTransactionId": "MT7850590068188104",
  "merchantUserId": "MU933037302229373",
  "amount": 10000,
  "callbackUrl": "https://webhook.site/callback-url",
  "mobileNumber": "9999999999",
  "deviceContext": {
    "deviceOS": "ANDROID"
  },
  "paymentInstrument": {
    "type": "UPI_INTENT",
    "targetApp": "com.googlepay.app",
    "accountConstraints": [
      {
        "accountNumber": "420200001892", // Optional. Required only for TPV Flow. 
        "ifsc": "ICIC0000041" // this should fixed as of merchant details 
      }
    ]
  }
}

this should fixed as of merchant details "accountNumber": "420200001892", "ifsc": "ICIC0000041"

and in the merchant id should be upi id of user

Can anyone please help me with this issue