Bad customer service

What a bad service that I received from Mtn. I called requested a tax invoice that was last week with ref ***. It is almost a week that I have been struggling to get assistance. I called today an agent answered a call and keep quiet without talking. I had to call again spoke to Nonhlanhla who told me that I have to call again as system is offline. I asked her why can't she take my number and call me as I wouldn't know when will the system be on line. She said she can't take my number I have to keep calling again. What a service,You guys don't know. Customer service. Mtn deserve a bells with bad customer service. The worst ever service