Paid $150 for an oil change, and my car says there...

Paid $150 for an oil change, and my car says there's no oil in it. My check engine light turned on, and the person who serviced my car didn't answer his phone nor did he return my call. The person on the phone made it sound like I was liable for their malpractice. I've been a customer for over 5 years, and in my experience they take very good care of you when you first buy a car from them. After that you're just extra work for them. Very disappointed.