first, make sure to repay the loan immediately, and make full repayment as far as possible. If you can't afford it, you should also repay the minimum repayment amount in full, which can prove that you are not maliciously overdue and have the willingness to repay.
after the repayment, you should contact the bank in time. When you call, you must explain that you are not maliciously overdue because you have misremembered the repayment date. If the bank has not reported your overdue situation to the central bank's credit information system, your credit will be restored and the bank will not record your overdue.
If the overdue period is too long, the bank has reported your overdue situation to the bank, which is irreparable, but you should also repay the loan immediately, and don't cancel the credit card after repayment. You know, the cancellation of the credit card will not eliminate the bad credit record. You'd better continue to use this card after repayment, ensure that you repay the loan on time every month, and cover the bad credit record with a good credit record.
In short, no matter what causes your credit card to be overdue, you must repay it in time when you find it overdue. If you are unable to repay it in one lump sum, you can negotiate with the bank to repay it. Otherwise, you may be sued by the bank if it is overdue for too long. At that time, it may be too late to remedy it.