Grade 3 arithmetic too much for FNB

What is 5 x R300 x 40%? Well that's easy you might say - its R600. Not so fast. For FNB and eBucks in particular this is an exceedingly difficult question. so difficult in fact its taken them 3 weeks so far to try and work out the answer - and the clock is still ticking. Is this the type of bank you would entrust your money affairs with? 3 weeks ago I purchased eBucks vouchers on which was supposed to earn a 40% discount. sadly, the discount was not awarded and I was overcharged. Despite raising it immediately with my own personal private banker I have yet to receive a satisfactory answer to my problem.