Can't change the volume on my CD player?

My Sony cdp-cx225 CD player doesn't have any apparent way to control the volume. My rm-dx53 remote control for said CD player doesn't seem to have any way to change the volume either. I looked at the online manual for both. It mentioned volume, but did not tell me at all how to change it. This is odd, because it goes in depth on how the open button opens it.Can't change the volume on my CD player?
I would either call the customer service line and ask for help---or get a new Cd player.