Gateway Modem Equipment Fee

If understand correctly, this fee is associated with the cable modem/router. However, I returned that device (Cox Solutions Store - Quail) in late November, or early December of 2013. They told me this fee would no longer be charged, so I'm not sure why I am still being charged for this fee. I'm using the phone modem to route internet via ethernet to the living room. The phone modem sites inside the panel box were the phone/ethernet connections are for the apartment.

I've sent an email to billing, but would like to hear feedback on what this fee actually is.

Thanks.