Turkish Airlines Didn't Process the Refund Voucher

Last November, my mother purchased a round-trip ticket from Berlin to Istanbul and back. In December, we changed the return ticket and paid the difference, resulting in a refund voucher worth ₺396.77. However, the refund process was not completed at the Sabiha Gokcen ticket sales office.
Since my father was not present and the card was in his name, we started the refund process later. We have been dealing with feedback and refund issues since December, and today is October 21, making it ten and a half months of ongoing struggle. They keep requesting documents repeatedly.
Despite sending the required documents multiple times, there has been no resolution. We feel humiliated and mocked with our own money!
Even though we have informed them that my father is a cancer patient currently undergoing treatment and my mother is also receiving treatment for her health issues, they continue to make us chase our own money! Enough is enough, really.

