FNB is sneaky and unfair

FNB was unfair to me. I wanted to settle a credit card beginning of the year they said the discount campaign was not running I should check in June. June came I asked for a discount they said there is no discount campaign, I settled the amount on 10 June, then 5 days later they send me an SMS that I qualify for a discount (which was +-R3000). I called in to ask if they could please assign the discount still so I could get back the R3000, they said no I shouldnt've have settled before. Why did they even bother sending me that SMS then after the account was settled. I asked if they could then give me a discount on settling the overdraft, they said no the discount is only for the cr card.