Cancelling contract proving difficult

I am trying for weeks now to cancel my contract with them, but no joy. Tried phoning many times and it appears the phones don't work. Sent an email many times and they do not send any replies. I tried being friendly for very long, but that did not work. Was promised though they will contact me once, but that did not happen. Really disappointed that I must get to this. If this does not work I will try and take the matter further after consultation with people that can assist me.