e mail not working

I have been having a problem with my outgoing e mails not being received by the people i send them to. I have phoned Telkom 10210 on four occasions to resolve this problem to no success. On two occasions i was promised that some one from their e mail department would call me. The last being on the 18 May 2015. I am still awaiting a call. I have had my computer at the computer shop and they say the problem is with Telkom. I have no wear ells to turn and their is no walk in center at Telkom to assist.