Although I have never encountered such a situation, there should be no problem.

First, you signed the parents' card. Of course, you should sign your parents' names, because parents are the owners of the card. From this point of view, the signature font is different and the transaction can be successful.

Second, you can use different fonts. There should be no problem with a typo. I don't know what the payment method of your parents' credit card consumption is, some by signature and some by password. The security code is usually used overseas (it is usually displayed on the back of the card and can only be taken out after the user remembers it. Some banks do not display it for safety, but only prompt it in the attached instructions when receiving the card for the first time). The bank has regulations that if the transaction is made by signature and password, the bank is not responsible for compensation. So you just need to make sure whether your purchase is successful. Some banks will call cardholders to verify some suspicious transactions, and they have the right to stop payment.

Third, you can call the customer service (the phone number is on the back of the card), and they will help you check whether the transaction is successful, and then talk about the situation and ask if there are any questions. Their answer is the most accurate.

Fourth, sometimes when you sign the words, the pen is not good, and when you run out of oil, you can only write the impression, and the transaction can be successful.

As for the supplementary card mentioned by others, it doesn't matter much, except that the name of the supplementary card is yours, and you should sign your own name when signing it.

I hope I can help you.