Frustrated at FNB Housing

I am writing this review in dire frustration. I received a call from one of the FNB Housing agents informing me that due to a payment reflecting late, I have incurred a charge on my home loan. The month in question was July. Please note that my debit order is set to go off on the 15th of each month and I can confirm with proof in hand that my salary actually came into my bank account on the 14th of July. The account had more than sufficient funds as I only had one debit order of about 4K that went off on the 15th as the rest of my debit orders go off on the 25th and 1st. My bank statement for the month of July clearly evidences this. I am not certain why this reflected on the 8th on FNB's side and I have a feeling there was a system glitch on their end. Whatever the case may be, as a customer I believe I fulfilled my obligation of ensuring there were sufficient funds in my bank account. I did not even receive a text message, email or call to advise of any amounts reflecting late so the call received today comes as a huge shock to me. I need FNB to sort this out as I'm not willing to incur a charge which actually ends up reflecting on my profile.