Akbank Charged an Annual Fee on My Fee-Free Credit Card and Refuses a Full Refund

I have been using an Akbank credit card for four years. Despite my card being fee-free, a fee of ₺796.50 was charged as an annual fee. When I spoke with customer service, they admitted that the fee should not have been charged. However, they offered to refund it only if I agreed to keep the card for another six months. This is both unfair and contradictory to what was initially promised when I applied for the card. If they can admit their mistake, why impose extra conditions to correct it? They charge a fee on a supposedly fee-free card, refuse to refund it, and then ask for a six-month commitment. I will be taking this matter to the Consumer Rights Arbitration Board.