Cablecard with an X1 4k set-top box

Hi - I currently use a CableCard with my own TiVo DVR. I just upgraded to the TV Plus cable plan where one X1 4k set-top box is included. 

Can I use both a CableCard and X1 4k set-top box without monthly fees? I believe I should be able to have no fees with one box.

Thanks!