Am I being scammed?

I took my car into the Honda dealership today for an oil change only. When I went in to pick it up, they told me I need rear brakes and wanted to set up an appointment for me tomorrow. (Funny, it took me a week to get an appointment for an oil change.) I told them I would set it up later as I couldn’t afford 165.00 right now. I didn’t think to ask until I was driving home, but how did they know I needed brakes by just changing my oil? Wouldn’t they have to take the tires off to see that my brakes are bad? Am I being scammed?