1. Even though you have dropped cheque on the due day, only if the bank realizes the amount with in the same day, if not bank can levy late payment charges.
2. If the cheque and credit card are from same bank (Standard Bank) they can consider one day delay in the payment, as you are not a defaulter.
3. If the cheque and credit card are from different banks, it would take 2-3 days for the bank to realize the due amount. even if they levy late payment charges, you can approach through customer care and ask them for removal of interest charges.