I signed up for xFi and was told at the store that 250Mbps service prevents me from getting my own modem. So, have a rented XB6-A. Can someone confirm if what I was told is true and explain why?
xFi Service REQUIRES that you rent a compatible Comcast Gateway.
I just checked, and for your plan specifically it does include, and require, the rental of an xFi Advanced Gateway (the XB6).
If you would like to use your own equipment, you would need to change your plan.
I hope this helps.