Nedbank Money App has no security feature

I accidentally selected the wrong number (MTN) while trying to recharge my Telkom Mobile number via the Nedbank mobile app. R40 was deducted from my account and my cell number was not recharged. I called the Banking call centre requesting that they reverse the transaction. I was told that I should contact it is not reversible. Nedbank told me that they could not help. I was extremely disappointed by the service I received from NedBank. It showed me that they are not willing to protect their client. There is no reason why they should not put a security feature on their app to validate if the cellphone number exists on the selected network. I want my money back!

Regards, Trevor