Having a credit card doesn't mean you will be paying for interest. Debit card has less promotion/cashback/rewards compare to credit card.

Side track a bit, I have a full flexi housing loan and I use it to receive my incomes to therefore reduce the interests (monthly rest, every last day of the month).

What I like to do is absorb as much as possible of my expenses in my credit card so that the cash can sit in my housing loan account longer to reduce the interest until the due date of my current month statement is up (usually i do it 3 ~ 5 days ahead) then I pay off my credit card balance.

To my surprise there are some purchases that can be done via an interest-free instalment plan. Instead of forking out that amount immediately, I subscribe to the instalment and end up I save interest on my housing loan.