xi6 installation

I need a wireless 4K box for one of my bedrooms (Xi6).  I am getting a run around from Xfinity.  I am told I can't order one unless I have their router.  I got their router.  Now they are telling me I have to have a technician install it ($70).  Why?  Does it have to run on their Wi-Fi?  I don't want their Wi-Fi as I have an AI Mesh.  One would think this was a simple as connecting the box to the Wi-Fi and let it call home to Xfinity.