FNB eBucks disputing the fuel purchased at Engen

Last month I spent R2300.15 on fuel at Engen. But FNB is saying that I only bought R1100 at Engen whereas I always buy all my fuel at Engen to get maximise my eBucks. This is really ********* for FNB to say that I didn’t buy fuel at Engen when all my fuel purchase is always at Engen. Please refund me the R411.80 as I bought all the fuel at Engen. You can check my bank statement for further details.