Ignoring my written request to cancel service

Help! I completed the online form on August 30 and was told "We're sorry to see you go, and we'll call you within a few days to ensure you really want to cancel." I explained in the form that I was NOT canceling, but I was moving and had already started service at the new house. I'd finally moved out of the house and needed to stop service. No one ever called and now I got a bill for the old house! HELP. I tried calling and it was worthless. Couldn't get anyone on the phone.