CANNOT CANCEL MY SERVICE

I submitted a form for cancellation of my telephone line at the end of November 23rd 2015. It is now the 12th March 2016 and I am still being charged for the service. Nobody lives at the address or has done since the 23rd November 2015. I have emailed the form on 3 occasions. No response. I have called the call centre 5 times and only once was told that it would be expedited to higher levels by a consultant called Monica Mashigo. To no avail whatsoever. I then went into a service centre and was told they don't deal with this. I have been online and left messages with a so called 'Talk to a friendly agent\ No reply! I am at my wits end !! What do I do now, I have another telephone line so if I just stop paying the one in question I will be cut off. Amazingly the one in question is being called and billed.<br> Please can someone help with this disgusting service"