Where do all the R7.70s go?

We have a seniors prosperity account with ABSA bank and as we have investments, all charges are rebated except for a few odd things. At the beginning of December they short changed us R7.70. It just wasn’t worth the hassle of going in to the bank, wasting money on petrol and parking and sitting on a hard seat for at least an hour with aching back and hips. We let it go. Fast forward to March 2018 and the same again; R7.70 short. As it is such a specific amount I decided to phone Galleria branch to see what it was. On the 5th March I phoned and spoke to Logie. She was very abrupt and told me to phone the call centre. I pointed out that every time I do that they tell me to phone the bank! I was told that she could not “confirm my identity” and that was why I must phone the call centre. This begs a big and obvious question; how will the call centre: confirm my identity” then? I have had dealings with Maureen, Phila, Rajen and Marianne at the same bank and they had no problem checking who I was. I have had the misfortune to talk to this woman before. Before I could draw breath to speak she hung up on me. Upon re-dialing I warned her not to cut me off again. She said she didn’t know anyone was there! So, if you are old, asthmatic, hearing impaired or have a speech impediment pray you don’t get Logie. She obviously has no patience. All I want to know is: what is causing the R7.70 charge so I can avoid it in future? Is that too much trouble? Why should I be inconvenienced if ABSA have made a mistake? Just explain it to me.