ADT Security Service Cancellation

I have been trying since August 2018 to cancel the ADT security service on behalf of one of my friends. He phoned and was told to sent an email - he does not have access to email (not everybody has access to email). I then sent an email with all his details, and still the service is not cancelled. I then phoned while he was standing next to me. They insisted on an email. I then created him a gmail account and sent another email. Still they have not phoned him to confirm the details and cancel the service. He would like to cancel it because when he needed the service, the security refused to come to his house. Apparently it was to dangerous. How may I help my friend to cancel this service, costing him a lot of money every month and he cannot even make use of it? Thanks. Adéle