Speeding fine which is not mine

I traded in my car last year September. Signed for it on the the 12 September 2023. I received in the post a speeding fine for my old vehicle that I traded in which took place on the 29 September. I received the fine in December in the post. And immediately contacted Hyundai the Glen explaining what had occurred. Why was the car still in my name a couple of weeks later? And I was promised that the matter would be sorted. Going about my business. On the 17 July 2024, I had received an sms that the fine was still not paid for, and I would receive a summons to appear in court. I had contacted the dealership again, at first they asked me to pay for it, and they would give me the money thereafter, which o declined, as I did not believe the matter would ever be sorted out. A week later and I’m still waiting for answers. I’ve dealt with Hyundai the Glen for many years and this is the worst service I’ve ever received from them.