MTN make it impossible to buy simple data through my bank online

I am trying to assist a 94 year old friend by buying data for her phone. She is an MTN customer. I wanted to buy R150 data every week for the year. The options to buy data are extremely confusing with daily, monthly and time limited options. Even a call to customer care did not give me a solution. Why is it so hard to just buy data on my internet banking app? A simple option is not there and it looks like all the data bundles purchased expire after a period. Impossible for an older lady to manage. She also had R400 "******" with a subscription for Mzanzi Music which was coming off her phone. She had no knowledge of this but saw her data disappearing and has had to take the loss. This is an impossible situation and I still don't have a solution!!