Data Bundle Refund

I bought a data bundle 2GB for R99 from the MTN phone app *141# but the bundle has limitations and can only be used for certain apps - not the ones that I need! But it doesn’t tell you that before you purchase (only afterwards you get an sms). I contacted MTN for a refund and they are refusing to refund me. It’s obviously an error in their system but now I have to pay for it! Not fair! If I don’t get a refund I will be moving to a different network.