If the passenger cancels a non-refundable fare, only taxes will be refunded. In this case, flight cancellation fees would be applicable. Said refund will be credited to the debit/credit card used at the time of booking.
The Turkish Airlines ticket refund request will be redirected to the credit card used to make the purchase and a cancellation fee may be charged. Please keep in mind that the refund processing time depends on the process of the credit card issuing bank. In some cases it may take up to 1-2 billing cycles.
If no part of the Ticket has been used, Turkish airlines refund policy you will be refunded the fare less the cancellation fees associated with the fare rule of your reservation, in accordance with the cancellation fees.
If part of the ticket has been used, the refund will be equivalent to the difference between the fare value of the ticket initially issued and the fare value of the used part of the ticket.
Source: https://www.qxbooking.com/blog/get-a-refund-on-turkish-airlines-flight-ticket