Turkish Airlines Ticket Suspension Fee and Incomplete Information

Today (August 27, 2023), I called Turkish Airlines customer service with my mother. We wanted to get information about suspending my flight to Frankfurt on August 29 (due to my visa not being finalized yet). The visa could be finalized on the 28th as well. I spoke with Ms. Ahsen, and she informed us that the suspension process would cost ₺4500. We mentioned that we could suspend the flight on Monday if my visa was not issued. At the end of the conversation, the lady said that this matter needed to be resolved at that moment; otherwise, I would lose my right to suspend the flight, and this inquiry could only be made once. If she had told us at the beginning that this process could only be done once, we wouldn't have proceeded with it since I am still waiting for my visa.
Additionally, as an Erasmus student, I bought the ticket with a promo code that allows for future changes under the PrimeFly program. When I change my open ticket, will my student rights under this promo code be preserved?
As a result, ₺4500 was paid, and if my visa is issued tomorrow, this will have been for nothing. To avoid losing my right just for asking a question, I had to suspend my flight and pay ₺4500 due to the incomplete information provided by the customer representative. This is a serious grievance, and I hope for assistance on this matter!