Thre things come to mind:
1. When replacing the clutch always resurface the flywheel.
2. If the service was done under warranty they do the minimum. I am not saying it is right, it's just the way they do it.
3. It sounds like the clutch is not fully disengaging. Slippage would not cause grinding when you shift.
Bring it back and tell them there is a problem with the way it shifts.
