No action has been taken on my cancelation request

I have requested a cancelation on my adsl usage on 18/11/2015.<br> I was told i will receive a response within 48 hours of my cancelation.<br> I re-submitted the request on 07/12/2015.<br> To date i have not received any response.<br> The call centre agents cannot help me as they claim that the cancelations department does not have any contact lines and the only way to get hold of them is via email.<br> I would like to lodge a formal complaint.