Turkish Airlines Ticket Rescheduling Issue

On May 19th, I purchased a round-trip ticket from Ankara to Izmir using a student campaign. On July 19th, I requested to reschedule my ticket. They asked me to pay a service fee of over 300₺ without any penalty for a one-time rescheduling. I agreed, but due to a system issue, they couldn't complete the process.

The call center said they created a feedback report and that I would be contacted. No feedback report was created, and no one contacted me. I called again on July 24th, and this time they asked for 500₺. I explained that I was supposed to pay 300₺ but couldn't due to the issue. They created another feedback report and I received an email instructing me to visit the sales office.

When I went to the sales office, the fee had increased to 900₺. The lady at the Ankara Sales office informed me in an unpleasant manner that the fee increases as the ticket price increases. Is Turkish Airlines a company that delays its customers by saying there is a system issue until the ticket price goes up? Why are you trying to make the customer pay for the increased ticket price when the issue was due to your system error? I am experiencing an attitude and behavior that I never expected from a corporate firm like Turkish Airlines.