Cannot Cancel My Booking.com Car Rental Despite Free Cancellation

I made a car rental reservation through Booking.com with Avis for a compact class vehicle to be picked up in Mytilene on 02/06/2026, under reservation number18554739012. According to the contract conditions shown during the booking, I clearly have the right to cancel this reservation free of charge until 30 June. Since 1 June 2026, I have tried numerous times to cancel my reservation via both the Booking.com mobile application and the website. However, every attempt ends with a technical error in the system and the process does not proceed to completion, so I am unable to finalize the cancellation myself. The payment of ₺4,546.17 is to be made at the counter, and due to this system error I am at risk of being charged the full reservation fee, even though I am trying to exercise my free cancellation right within the specified period. I also tried to reach customer service, but I could not get through and therefore could not resolve the problem via support channels. As I am unable to complete the cancellation due to this ongoing technical issue, I request that my reservation be cancelled free of charge, that no fee be charged to me now or at the counter, and that written confirmation of the cancellation be provided to me.