There is no way we could ever diagnose a the cause of a problem here online...
So, with that in mind. This thread is here to provide you a way to escalate your concern. Pete has no say in whether your car is ultimately fixed. So take this thread for what it is...
You have to convince GM that there is a problem. I will say that GM has replaced multiple clutches with a similar problem.
So bottom line,
There is no need to get upset here.
If you want to be angry with the dealer then so be it.
But in the end this is a vehicle to help you get resolution. Not a guarantee.