FNB Refunds very slow compared to other banks

My question to FNB is, I had 3 refunds due by Temu with FNB and 1 with Capitec, why is it that my refund to Capitec was processed already but FNB keeps on telling me after i send them the RRN numbers from Temu that there is no refund showing that must be paid in my account. Please explain how FNB can be so slow to Capitec because im seriously considering changing my salary bank back to Capitec