Mtn poor custormer service

I took a contract phone online, they delivered the phone on Tuesday 25 August. I started using the phone the next day and I put 2 sim cards as the phone is a dual sim. I struggled with the dual sim settings which does not appear at all, I called Mtn South Africa they told me that they closed the other slot so I can only use 1 slot I tried to explain to them that I took a dual sim phone because I needed the feature, they said they can not help me I must use the phone as it is. I have not been able to use my other sim card which is the most busy sim card with all kind of calls to receive, for the past 6 days I have not been able to use my sim card and surely I have missed many calls, I am even expecting calls from companies where I app**** for job. I am very disappointed with their service, unfortunately they did not explain anything with regards to this dual sim phone for their contracts I only noticed when I started using the phone and got this terrible explanation when I called them.