Unresolved License Fine

I am extremely upset. I sold my car to We buy Cars in 2016, while the car was in their warehouse the license expired which I was not aware that they did not renewed it. I got a new car only now in 2022 and when I wanted to put it on my name there was a outstanding license fine of over R2000, I had to pay it due to my roadworthy certificate that was only valid for 30 days. If I had not done so I had to do a second roadworthy and pay R500 again. I am now stuggeling more than 2 months to get my money back from We buy Cars as I feel it was their responsibility to renew the license as the car was in their posession. After numourous emails and phone calls the issue is still unresolved. I am extremely disappointed.