General Motors review: warranty

I took my Chevy Sonic LTZ Turbo the the dealer on August 28, 2019 with transmission problems. I later spoke to a techinician there who gave me a brake down of what was going on. He said something about the engine and turbo and never mentioned the transmission. He later said it would not be covered and I should contact my insurance company and have them total the car. They said there was sludge and that the turbo need replacement. I did not have the car serviced at the dealer I took it to a local midas. They did all the maintenance. They said there was some discrepencies but with the way they reported in carfax.com. I did what I was suppose to do, service the car. I was never told that in order for the warranty not to be void I needed to go to go to dealer. I did what I was suppose to do, service the car. Its not my fault there was sludge or that the engine did hold the the way it was suppose to. I did my part! Now no one want to take responsibility!