How do you cancel a landline-person is deceased

We have been trying to cancel  landline since June of this year. 

We have spent HOURS on the phone with 'customer service'..no help..no one has records..no idea what number is, agents hanging up. I have sent Death Certificates, and made countless attempts to rectify this. BUT STILL GETTING BILLS!!!!!  FOR A DEAD PERSON. 

I have no other choice to go to our local news station, and publicly humiliate your company for charging a dead person  3 months after her death.. AT&T -you should be ashamed of your operations, not 1 person in the last 3 months has been able to help me cancell this service- Literally hours spent trying to resolve