Forced exercise of options in an IRA

I hold an IRA self-directed account with one of the largest broker-dealers/investment advisors in the country. Recently, a cash-bought covered put expired in the money in my account. When I looked at my transaction history, it turned out that the put was not exercised but instead forcibly sold without any warning for less than its actual value with a substantial additional fee assessed. So far, the broker-dealer has refused to admit fault or do anything other than refund the fee. My loss is small, however, I am concerned that this broker-dealer is bilking other small investors out of their money the same way. Other than filing a complaint with FINRA, what else can I do? Thanks.