How does 2.88 months become 6 months

I purchased goods to the value of R1 546 on the 25 August and returned the goods on the 2 September . I also purchased a Cellphone on the 23 August also 6 months. My balance is R51823 with an installment o R1825. If that Installment is divided into my balance it works out to 2.88 months. <br> <br> The problem is I get asked over 6 or 12 months. Simple mathematics says that Foschini's Billing doesn't cater for that or additional purposes because they never ever adjust a higher Installment but you could end up paying off your items in 1 Month in some instances obviously to there benefit.<br> <br> I have other store accounts but Foschini is the only one that doesn't make sense. Explaining to Natasha in Customer Services was a total waste of time. I also was not explained the Cellphone Plan. Obviously, I must not buy a Cellphone at Foschini in future.