DISCOVERY CARD - DEBIT ORDER PAYMENT ALLOCATION TIME DELAY

I have had my discovery card from just about the time it was launched but over the last few months I am having issues with them. Whenever my credit facility is low, I do an EFT before 3:00pm from my personal bank account and the very next day my credit facility on my Discovery Card is increased by the amount I pay. However when Discovery debits my outstanding balance on a monthly basis, even though money is being debited off my personal bank account the credit on my Discovery card only reflects 5 days after the debit order date. In that time I have got embarrassed many times at retailers as it showed I got insufficient funds or I was unable to make purchases on my credit card as my credit facilty was not increased by the debit order amount. For Discovery, which is at the forefront of technology, 5 days to allocate my debit order payment is simply unacceptable. It also means I cannot make purchases for 5 days - what is the point of having a credit card. I requested to cancel my debit order and that I make EFT payments for outstanding payments but unfortunately that cannot be done. In the past if I made payment via EFT on due date, Discovery also debits my account- I eventually end up making double payment. I spoke to one of your managers today and told them about my dissatisfaction and instead of trying to find a solution, they were ever willing to let me cancel my Discovery card. Please find a workable solution for me or I will cancel my credit card