Unhappy customer

Today I called in the Discovery Call Centre to find out if I will be getting the August month cashback since my contract was cancelled on the 26th Aug. I was advised that I will not be getting it since my contract ended 26 Aug not 30th of the month. I find this as unfair cause I was with discovery most of the month accumulating points and spending petrol. I think forfeiting the benefit just because of 3 day before month end is unfair and would like my benefit to be at least calculated pro-rata, just like they are able to do pro rata calculations for installments that must be debited from my account. i do not understand why i should not benefit as most of the month i was active it is only 3 day that i was not active. i have always spoke well of discovery and even recommending it to friends and family, i am so surprised by this since i have been with them for along time. i think i do deserve to get my benefit and it should be calculated pro-rata.