What must happen now

There is plenty we can do to avoid some complains… On the 13th May 2019 I send an email requesting a callback to update banking details on my home loan account, got a reply back to the email which said I would get a call back in 24 ours which I didn’t. In the meantime I personally tried calling the call center which I was kept onhold for over 5 minutes on each call. So yesterday I had a chat on the app with Xolisa who assured me that I would be called back, still no call. I went on the App again today Nonhlnhla called me back and tried to transfer me, still I couldn’t get through I went on the App again and Precious advised that for some reason she cannt call me to transfer I need to call in, she finally called once I mentioned I was going to complain. She called back at 17.02pm homeloan department is closed at that time. What must I can do now because I am not getting any help ?