Cancellation issues

On 4 Jan I cancelled a landline that was in a business name for which I was the responsible person. The cancellation was not loaded. This line has not been used at all since then, yet I am being invoiced for it. After much being sent from one person to another, I got someone who eventually explained there is a cancellation period. The time the cancellation was eventually loaded was days after it should have been. One person told me 30 days, the other 30 working days, and yet another 20 working days. And then the cancellation wasn't even done properly. It was also loaded with a different order number than the one I was given originally. They couldn't even find my original cancellation on the system! I need the cancellation finalised, and I need the financial dispute resolved. I can't be expected to pay for a service I am not using.