Hostmaster not responding on mails

I am having a problem with my incoming mail which is bouncing back, outgoing mails failing. I called Telkoms 10210 and was transferred to the technical 2nd level support. This has been going on from Friday 31 July. I was told that they cannot assist me as they don't deal with domains which is registered ! I was told that I have to email the hostmaster and wait for a response. Problem is they don't respond at all!!!!! No one at Telkom is willing to help. As a business emails are critical for us.But they simply don't care... Please can someone advise if there is an alternative way to contact the hostmaster??