insurance advise

My 72 year old mother purchased her car insurance thru the same insurance company as the one I had before she moved in with me (5 years ago). About 3 years later she drove into a ditch in a snow storm, but was physically unharmed. She filed a claim to get some minor damage repaired on her car. Her insurance automatically went up afterwards (as was expected) and so did mine, but they told me that my insurance was going up because of my credit report (which I didn't dispute). About 6 months later, my mother got rid of her car and cancelled her insurance. Now, a year later, I just found out thru my agent that my insurance company was charging me a higher rate because they added my mother onto my policy without me asking them to do this and without notifying me. They just "assumed" that since she lived in the same household, she would be driving my car, is what my agent told me. What, if anything, can I do to fight this?