No service and no reply from customer service

I have bought a Samsung S21 Ultra 9 months ago I was making a call and when I want to hang up the phone call the screen of the phone just went black. I have contacted customer service and told them what happened. I also told the representative that I have bought the phone cash and I lost the proof of purchase. The representative at customer service said I must book the phone in at a repair center and then I must contact them again to give the details of the booking number. Ref for the call to Samsung is ***. I have called Samsung 4 times and every time they said they will call me back after they have spoken to there manager. I did not received a mail a call back or any type of communication from Samsung. They just promise me they will call me back with an answer but nothing. I can't believe this is the service Samsung is giving a customer that has bout a top of rage premium cellphone from them. The phone is in 10/10 condition with the box and the ICASA sticker on some plastic still on the phone at the service center at the moment now going for a week and no reply.