Underground Comcast Line Locating

I have a contractor that's going to do some drainage work on my property that will require digging.  The contractor submitted an 811 request (I'm in Illinois so it's called JULIE) for utility locating, but my Comcast line was never marked.  According to JULIE, they have no record of a Comcast line on my property even though I have Comcast Internet service.  How do I get their records corrected so my Comcast underground line can be marked?