Nobody gets back to me

I am dealing with this company for a few years now where I was paying off an old vodacom account. Vodacom offered me a discount in October and I have been calling this company since then to ask them to settle this account. Nobody gets back to me. I went to the extent of email the directors and I still am not getting joy. Nobody calls back. The service is appalling a ND the only next thing that I can do is stop the payment.