Unresolved Refund Issue with 'joom.com'

I bought a thermos for 314 TL from "joom.com" on June 2, 2023, but after it arrived at the Dongguan distribution area, it never went anywhere else. They said they couldn't cancel the order because they already gave the product to the shipping company. I got a message saying I have to wait until August 25, 2023 as a legal deadline. Well, I was waiting. After the deadline was over, I reached out to them and they said they processed the refund and gave me a code to give to my bank. I called the bank and gave them the code, but they told me that there haven't been any refunds from "joom.com" in the last four months. I reached out to the website again, and they requested a signed and stamped account statement. Even in that, they didn't have any record of the refund. They keep saying that they checked it again, gave me a refund, and gave me the same code. They're saying I should ask the bank for an official document if the code doesn't work. The bank says they can't give you a document for something that never happened. I keep telling them that "joom.com" should give me official proof that they processed the refund; it's my legal right. They're saying they can't help. Basically, I think they didn't give me a refund. They're not telling the truth.