Unjustified Charge for Cabin Luggage on SunExpress Flight from Antalya to Leeds

I had a flight with SunExpress from Antalya to Leeds on July 26 at 1:00 PM. I was entitled to a carry-on bag and 5 kg of checked luggage. At the counter, I checked in my luggage and received a tag for my cabin bag. After passing through three security checks, just as I was about to board the bus to the plane, a staff member, whose name I later learned was A*** U***, told me that I needed to pay for my carry-on bag.

When I asked why, he couldn't provide any reason, and when I showed him my cabin bag tag, he accused me of possibly attaching the tag at home or taking it from a friend, effectively accusing me of lying and theft in front of everyone. When I asked how much the charge was, he said 70 euros. When I questioned how this amount was determined, he became aggressive towards me and my friends.

I have been unable to reach SunExpress to resolve this issue. If the matter is not resolved, I will initiate legal action for the insult and financial loss I suffered.