hbo max back charges

I have been a internet-only subscriber of xfinity for two years. Apparently in the third month or so of service, an HBO Max charge was added onto my account at $15/month. I have no idea how or why. I was not made aware of this and because of my automated payments, did not realize my bill had changed. In other words, I have been paying for an HBO Max account that I didn't know I had and have not used a single time for over two years, to the tune of almost $400. Is there any way I can get any of my money back or perhaps get free access to it for a time period now that I know I have it? Any help is appreciated.