Standard Bank
Charged unpaid fee twice

I wrote to Standard Bank asking them to Stop Payment to MTN. They charged me R40, then the following day they charged me R115 for unpaid fee. Why must I pay them twice for one thing. I also called the branch asking them to stop the MTN payment because i could see that it was not returned. Standard Bank is just reeping us off. Why must i pay R155??? that is too much.