Rohan Motors — Car first service

I am not satisfied with my first free car service because company charged me high payment for only engine oil. Even I don't know which engine oil they put in my car. I didn't see from where he take engine oil and they also not tell me any thing about engine oil. In front of me they put allready open engine oil. When I ask this is not packed or seal tight they told me that it's come allready how can I trust that they put good and new engine oil in my car.
I am very disappoint regarding engine oil they put in my car.