Stopped Debit order without my consent

My personal loan debit order was stopped in January without my consent. I called on the 11th of December 2014 to change the debit order to the 15th of December as normally in December we get paid early and that was processed accordingly. In January 2015, no debit order went through and I called to enquire, the consultant promised to call me back and did not. Since then, I have been trying to contact them without luck, on the internet, via email or their contact number. I requested monthly statement as now no debit orders were going through on my account. To my surprise I get an email from Sanclare (Debt collector) in July demanding payment. I relate my story to try and sort the issue, they promised to look into it and revert back. To date no feedback and I have now received a very threatening text message from VVM. I want to know why the debit order stopped which has also affected my insurance on the policy. I am now in arrears yet it is not my fault. My name is now on Credit bureaus for defaulting yet I am not wrong. Who instructed them to stop debiting my account and stop sending me monthly statements?