Worst after sale customer service

I bought a car from them in June 2023 and received all the documents. Now when I try to renew a license disc for my other car that was not bought from them, the license department tells me that the car I bought from we buy cars has license registration penalties. I told them about this and they responded by email to say I am liable for the car license registration and I am the one who registered the car late. Now the problem is when I got the car the license disc renewal was already done by them in May 2023 prior before I bought the car and should be done again in May 2024. And the car registration to my name was done by them and they gave me papers in July. Now which penalties do I owe. When I phoned customer care to get clarity, the lady tries to transfer me but noone is interested in taking my call, she ended up saying a lady called Shein will call me, I have been waiting ever since. The penalties might not be a lot of money but it's about fairness, honesty and doing the right thing to keep your clients happy.