Myntra.com — Refund not transferred into my account

I had bought a HRX shoe which was returned to them. Since it was cash on delivery I had to give my account number. Bymistake I gave
PPF account number. Myntra says that they have refunded my amount on 14dec 2020 to PPF account. However when checked I have not received any amount. I have given them the statement in which no transaction reflects. I checked with the transaction number which was provided to me by Myntra with my SBI home branch, they also confirmed of no transaction as such. Since it's a PPF account no one would be able to deposit or transfer amount into that account unless the account holder himself does that. Myntra denies of this reason and they have closed the complaint without refunding my money.