6 months to change a debit order?

I have requested my debit order to be changed to my new bank account in January.<br> Netstar have confirmed the change. Now I am receiving calls from their debt collections department claiming I have not paid. Last month my account was brought up to date and nudebt confirmed the change had been made. Now once again I see my debit order has not gone off. How many more times must I send the new banking details?????<br> <br> How can I trust you to track my vehicle if this task is beyond your comprehension?<br> I no longer want the order changed, I simply wish for you to remove this garbage from my vehicle and cancel the service with immediate effect.