MTN *****ing airtime

I bought R75 airtime from my banking app and wanted to convert it to data (which is R70). Had no other apps open or running on my phone. Then it shows I have insufficient airtime to load the 1G. A few seconds after buying R75 airtime for a weekly 1gig data bundle? ****************. I would like to know what MTN does with the money they snatch from us because this is really unfair!