Vitality don't update bank details - good luck finding the money!

On 3 APRIL 2019 my husband (ONLINE) changed our Medical Aid AND Vitality cashback bank account from an ABSA account to an FNB account. On 30 May, after not receiving our whole Kulula flight cash-back, we followed up. And guess what? Discovery did not do the update on their side - a lot of excuses, but no proper explanation to start with. We've made NUMEROUS calls, logged numerous tickets, and Discovery Vitality pleads ignorance - but, they will be happy to load ANOTHER ticket (which takes....o wait....they never come back to you on it.) Apparently the fact that THEY didn't change the bank details on their side now means that we have to figure out where the hell the money is. Which effectively means that I have to write off in excess of R2000??? Useless useless useless.