Bad Service on Cancelling a Line

I work for the Dutch Reformed Church in Rondebosch, Cape Town. I have been trying to cancel a Private Line with Telkom (a special audio line between us and an old age home down the street to broadcast our services to the home) we have had for years. I started this struggle in May this year. After many phone calls and many times following up...to no avail has this cancellation been done. The problem is...we have not been using this line for over a year now...and I am still paying for it. How in the world can I get this cancelled. I have filled in and sent all the correct forms and e-mails. Does any one know what I can do?