Bad customer Service from Mtn

I had a call with Sethu Qotoyi from mtn which was a very bad experience for me..I have been using My For all my life but bad service is what I can't tolerate ....I did extra time which I did not receive when I asked Zethu she told me about internet connection that I connect which doesn't show how much it charged me ,she couldn't explain my call log in detail.i tried asking for her supervisor or line manager and told me that no one is available to assist me . .her supervisor was not in later she is in the kitchen but I ended up not getting any help and my money gone ,money that I have to pay for after wards because I was billed for doing extra time ...can one one line manager contact me so that I can get a clear explanation of what happened to my airtime....to make things worse when I asked Sethu her surname she said Mtn ,it made me mad cos there is no one with the surname of Mtn ...if MTN continues with incompetence agent like Sethu ,who doesn't know their products then Mtn's name is getting ruined....