Petro card charges doubled without notice

I have an FNB Petro card which is linked to my credit card. All the pricing guides online tell you that it costs R25 per month (for platinum card holders)<br> <br> Out of nowhere this month without any notice, the charge is now R50! While this may not be a lot of money - it is the principle that bugs me.<br> <br> FNB - how can you charge double for the same thing without notifying your customers?<br> <br> See the following for a history of charges for the Petro card: [URL Removed]