If you only use online banking, it is not possible because it is across banks. Bank of Communications' credit card can be bound to Bank of Communications' debit card

And inter-bank transfers require handling fees.

If you want convenience, you can use online intermediaries such as Alipay to repay. There is also no handling fee.

I only know Alipay, so I’m just talking about how to repay using Alipay.

If you have Alipay, just log in to your Alipay homepage and click on repayment. You don’t need to open online banking for your debit card. If you don't have Alipay now, just register one.