In modern society, credit cards have become an indispensable part of many people's lives. But sometimes, when you try to use a new credit card or make a purchase on an existing credit card, you may encounter an "unsigned" error message. This means that your credit card has not established an effective contractual relationship with merchants or banks.

First of all, it is possible that your bank card is not activated. After receiving a new credit card or replacing an existing credit card, you need to activate your bank card according to the instructions on the card. If it is not activated in time, the bank may continue to leave the card unsigned, which will cause problems when conducting transactions.

Secondly, your credit card may be frozen. If your credit card exceeds the credit limit set by the bank or you delay payment, the bank may suspend your credit card. This will cause you to receive an "unsigned" error message when using a credit card.

Finally, you may not have signed a contract with the merchant. Some banks or businesses may require you to sign an agreement before using a credit card. If the signing work is not completed according to the agreement requirements, you may receive an "unsigned" error message when using the credit card.

In short, when you receive an error message of "Not Signed" when using a credit card, you need to contact your bank or negotiate with the merchant in time to ensure that your credit card is in a valid state.