Inactive Equipment Charge

Hello, I’m currently an Xfinity internet service customer for a few years. I recently noticed my billing statement showing a fee for an inactive flex box that has been in my possession and I will be returning. I was informed this is for a Flex device. I think I received this a couple years ago FREE from Xfinity. I was  never told it was to be returned nor I never received any type of notice, No message, No Email, Nothing about any changes or even a notice about it being inactive. Xfinity knew the box was inactive and instead of reaching out to inform their customers about the equipment they are taking advantage and instead charging us fees, when all of this can be avoided will proper communication! I never used it. Can't even say for sure I received it back then. I will be returning the box, but will like to know how I can receive credit or refund beings though this was “CONSIDERED FREE” when I first became an Xfinity Internet Customer.