Hi,

The information brochure of NTA NEET exam says that  " For cancelled transactions, the amount will, automatically, be refunded to concerned credit/debit card after the last date of online submission of Application Form or the process of Fee Reconciliation."

However if your transaction was successful and you got the confirmation page for fee deposited and complete your application process. In that case once fee submitted can not be refunded.

Hope you find it helpful.