Charging Double on Service Fees

I have a savings account with FNB, I'm on (pay as you use) price plan, whereby the bank charges per transaction and then debit the full charges on the statement closing date. I've come to realise that FNB collects the service fees per transaction and then collects it again as a once off fee on the statement closing date. I queried with their call centre (telephone banking), I spoke to 3 consultants, 2 of them agreed with my analysis but one didn't. The one who understood (Tshepo Kalaki) transferred me to another department for resolution but I was transferred back to telephone banking, I spoke to Garry who had no clue what he was talking about, I demanded to speak to Tshepo, I was transferred but the call was re-queued back to available consultant because there was no answer. I then spoke to Kopano Sebothoma, she understood what I was talking about and then put me on hold for more minutes to seek clarity. I hung up because I spent 44 minutes on one call on such a simple matter. I sent an email to the department and the complaints one but to this point I got no response. All I need is for FNB to explain why they debit service fees twice.