Still being charged after account is cancelled

I emailed Openweb over a month ago to cancel my contract, giving them 1 months notice. I received a ticket number and was told to also inform cancellations department which I did. Now over a month later they are still charging me for a connection I am not using. I have given them the legal one month cancellation requirement but they still refuse to cancel my contract because their internal system have in one particular department that claims they have not received my request even though I have the proof they have received it. There is no one to talk to - no phone numbers and no guarantee that anyone will reply to the email to cancel my contract.