Disgusting customer services

last year November, i called the ADT customer services to cancel my account as i was relocating and didn't require the services anymore. The agent i spoke with never told me to send the notice in writing. I called again in December after they attempted to deduct monies from my account, and i was told to send the email of which i did on December. Agent called Sithembiso Dloldlo called me and advised that i need to pay off settlement amount as i was in contract with ADT, i asked them to credit the my account for the monies deducted after the notice was sent and also for increments that was charged twice in my account. He promised to come back to me since January 13, until today i still haven't received the feedback and way forward. main concern is that ADT will mess my credit history whereas the mistake is on their side. I feel that this kind of customer service is uncalled for . PLEASE can someone who knows how to deal with the customer contact me .