Billing Issue

After my service went out and trying all the usual troubleshooting, I called technical support.  We repeated all the same troubleshooting and the agent said someone would come out to replace the cable box (which is a Xfinity rental).  I asked if there would be a charge for the visit and was told there would be no charge.  Wanting to make certain of this, I asked again and the agent reconfirmed that there would be no charge.  The technician did come out and spoke no english, making it very difficult to communicate.  He used his phone for translation.  After looking around outside, he eventually came in to the home and changed out the cable box which restored service.  Well, I've received my bill and there is a $100 Home Visit Fee on it.  I cannot get through to a live person to assist in getting this charge credited.  I am a long time customer and am very frustrated and disappointed at being charged a visit fee after being assured that there would be no charge.  How do I get this issue resolved?