Purchase 2nd Hand Car but Seller not help to transfer RC

I purchased a second-hand car and made the payment. However, after that, the seller did not transfer the RC (registration certificate) to my name. When I pressured him to do the transfer, I found out that the main owner of the cab was someone else. The person I bought it from had purchased it from Car24 and had not transferred the RC into his name. I spoke to Car24, but they said they could only provide information to the person who purchased the car from them, not to me. The insurance for the car has also expired. Now, I want to get the RC transferred to my name, but I don’t know the main owner or how to contact them. The car is registered in Delhi, and I live in Delhi. The person I bought the car from has his phone switched off now, but his home is in Himachal Pradesh, where I am from. I made the payment to his wife’s account, and I have the details of that transaction. I also have WhatsApp chat records where he kept giving me new dates, promising to get the RC transferred, but it's been almost 7 months now. Please guide me on what I should do."