Breach in service agreement

Two years ago and up until October this year my debit order went off my account as per debit order monthly. Today I get informed by ADT that my account is in arrears and overdue. They advised that they don't have my banking details on their system. I was shocked to say the least. They call centre clerk said she is also not sure what happened to my banking details. I then asked to speak to an accounts manager only to be told that such a large company as no account managers available to speak to me. Once again shocked to say the least. I then get told that they will come back to me after a shortly to let me know what happened and why my accounts which had a debit order for the last two and a half years now suddenly does not even have my banking details. Still awaiting the managers call which was meant to be shortly. Now I have an account that's in arrears due to no fault of mine. I have my ADT contract currently and all information together with banking details reflect. I need answer as to why this has happened together with information on who changed and cancelled my banking details without my consent. From a CPA perspective I think that ADT is at fault and is not delivering.