How can the other party’s insurance put me at fault even though my insurance found me NOT at fault

So I was shopping around for new car insurance today and the agent told me that I had an at fault accident which was news to me!!

So 3 years ago when I was 18 driving home in my Honda from school going through an intersection with a green light and two lanes going the exact same direction. I was in the left lane, and this tesla was turning right on red and accidentally over turned into the left lane T-boning my car. The side of my car was slightly dented and scratched but the whole front end of their tesla was destroyed. I didn’t know what to do but the driver who was EIGHTY NINE YEARS OLD refused to talk to me and made his son get out and exchange insurances and his dad’s license with me, and then told me to go home. So when I got home I told my dad what happened and said I was gonna file for damages but my dad told me that I should just let it go because my car was a sh**box and didn’t need a scratch fixed, and made me feel bad for the old man driving the tesla. So i didn’t file, months later i get an invoice in the mail saying that they were claiming I WAS AT FAULT? And i owed them $12K and that i was uninsured, which was OBVIOUSLY a lie because they got my information through my insurance that i gave them. It was a whole process and i was so young and had to basically figure it out on my own but I told both insurance companies what happened and my insurance company said that i wasn’t at fault and they weren’t gonna pay for the teslas damages. However i find out 3 years later the teslas insurance DID find me at fault and that claim is still effecting my insurance today. And apparently i have and had no legal ground to fight that accusation because i never filed a personal claim to get the damage they caused on trashy Honda fixed all because i was trying to do a good deed and promote good karma :/ This all seems so unfair, is there anything I can do? Or at this point should I just forget about it and deal with paying higher insurance rates.