H&M Did Not Refund Me for My Prepaid Card Orders

I am writing to report an unresolved issue regarding two refund transactions, neither of which has been credited back to my card despite considerable time having passed: a refund of ₺1,490 from ZARA dated May 22, 2025, and a refund of ₺2,998 from H&M dated May 15, 2025. Although both brands claim the refunds have been processed, I have yet to receive either amount. H&M stated that due to "operational reasons," the refund failed on their end and mentioned using Iyzico as a payment intermediary. However, they refused to provide any actionable support, claiming that I cannot contact Iyzico directly and that they themselves are unable to follow up further. ZARA, on the other hand, insists the refund has been completed and has closed the case without further explanation. Both purchases were made using a Denizbank prepaid virtual card. When I contacted Denizbank, they confirmed that no refund transactions are visible on their system and advised me to initiate a chargeback. Unfortunately, the "Transaction Dispute" section on Denizbank’s website does not support submissions for prepaid virtual cards, leaving me with no way to proceed. This situation has caused a financial loss of approximately ₺4,488, and it has now been nearly a month with no resolution. I urgently request: (1) immediate refund of the outstanding amounts, or (2) a clear, documented statement showing that the refunds were successfully processed, and (3) a viable method or assistance in submitting a chargeback for prepaid cards. If this issue is not resolved promptly, I will escalate the matter to the Consumer Arbitration Committee and pursue all legal remedies available. Thank you for your attention, and I kindly request your prompt assistance.