Demarco08

My 2004 gmc sierra 1500 sle , transmission started slipping I took it to a transmission shop in New Jersey I paid 3500 for the transmission to be rebuilt . 6 days later the transmission line running to the radiator popped off while driving I instantly pulled over and got it towed back to the transmission shop I was told the line blew to pieces but it’s fixed come get it two hours later it’s back to the original problem slipping 3/4 gear , I called the transmission shop and there making it sound like when the line popped I damaged the transmission when it popped I pulled instantly over I took it to another shop just now got it towed and they said it sounds like they messed something up and want to charge more money to fix it what do I do and how do I find out every step they took and aren’t they liable