Black screen after sending for repair in Mac

Recently send a functioning MacBook Pro to Apple store to fix the keyboard, but received a non functioning and black screen MacBook Pro in return. The Apple store stuffs doesn’t want to take any responsibility as I sign some data protection thing and asking me to pay for repair which cost nearly the same as a new MacBook, to fix the MacBook they broke for me. Is there anything I can do other than buying a new MacBook?