Kia Motors complaint: Engine replacement denied

I recently bought a 2014:Kia optima turbo. 6 days after I bought it the motor seized on me while driving home. I had a mechanic look at it he thought it was the starter. Took it off had it checked and nothing was wrong with it. The next day I found out ab all the recalls. So I called kua in Dothan Al and they said to bring it in. I took it in and he said they would have to charge me to 300 to hook the starter wires back up before they could diagnose it. Then he called back 2 weeks later said he needed any proof I had that the car had been maintenanced consistently. But I only had the car for 6 days. I have a receipt from the dealership where they bought 6 gallons of oil and an oil filter. He said that wasn’t sufficient and they will probably deny my claim. And that it would cost me another 300 to diagnose and tell me what’s wrong with it bc he would have to take the top of the motor off. My understanding was that the extended warranty covers the diagnosis. So why is he charging me $600. I really need my car. Kia needs to figure out a way to protect 2nd owners bc it not fair that we have to cover the cost to fix their faulty engine bc of paperwork they know we can’t provide. Feels kinda like they’re trying to avoid replacing whatever motors they can brc that they have sold so vehicles with several different recalls. How can I get my engine replaced?