Poorly designed App

I am a business client and I have repeatedly topped up my data over the past 2 years by Buying airtime then choosing a suitable data bundle. recently, I started using the MTN. That is where everything started going wrong.

I bought R300 airtime to buy an in app special. When I used the app, the app did not allow me to use airtime to buy the bundle, only my bank card. This ahs never happened to me before. A call was logged two weeks ago and I never heard back from customer care. I elected to use my bank card and asked for the R300 in airtime to be refunded to me. I have not heard back from MTN.

Last night I decided to use R99 airtime to buy a 10 Gig work from home bundle again on the app. This bundle did not connect and I cannot use the data. Customer care informed me that it is a bundle that is not available for top up, only for prepaid. It was allowed on the app. As a customer, how do I know what is allowed or not allowed when it is an available offering on the app?

The app has major design flaws and I don't believe user testing was done before it was taken live.

Pleas reverse the 10 gig I purchased and please refund me my R300.

I do not want any further top up bundles from MTN because I cant actually buy and use the bundles.