Super frustrating trying to cancel service

How exactly does a person cancel their service my 2yr contract is done and i want this thing off, emails to numerous addresses i have left messages on the phone line as there is never someone to speak to. I have always given my acc number and stated i want my services disconnected, now i get a sms you well deduct the debit order I have really only experienced good from this company until now you have really dropped the ball, the sales agent would call back in minutes whenever there was a enquiry now i want to cancel my service you get ignored!!!!