Turkish Airlines Ticketing Issue - Price Increase for Rebooking

In February, I had a ticket with Turkish Airlines that I put on hold, intending to use it between August 7-12. When I called to book the tickets, they issued tickets for both my wife and me, charging ₺3,500 per person. However, they did not issue my ticket due to a system error and later refunded it.
When I called again for rebooking, they quoted me a new price of ₺3,800, stating that it would increase. After another call, they demanded ₺5,000! Are you kidding me? Why should I pay for your mistake? The original price was the same when I first purchased it. What difference does it make to have an open ticket?