Can you pay one credit card bill with another card?

I think it depends on how the balance on your Grab card is made of. If it was top-up from other card, you would not be able to transfer it to a bank account as "cash". But if the balance is there because someone transferred money to you with Grab card, or your widthrawed from the Grab invest, then the balance can be transferred to your saving account, so as to pay credit card bill. I don't think you can pay DBS credit card bill directly with Grab card.

Not sure what is grab card, but can try to put the grab card onto AXS mobile? And pay credit card with it, I did not tey before, just guessing