Online data purchase backfires!!!!

I purchased 5gb data using the Telkom App and my bank card. Paid the R99. The money was deuctrd from my account, bu no data. I phoned telkom and they said I must ask the bank to reverse it!!!!!! The bank refuses to revese as it is an online purchase, as well as it was purchased through a secure portal. Why do you offer to people to purchase data, but then cannot when it doesn't work, then nothing is done. I have ourchased on numerous occasions online data and never had this problem.