First name contains invalid character
Today when I wanted to update my APP, it says "Verification Required". Then it jumped to Account Setting and says "There's a billing problem with a previous purchase. Please update your payment method." After I checked all information and clicked the Done button. It shows that First name contains an invalid character. the First Name part and Last Name part are highlighted in red.
I've been using my account for about two years, and I never had this kind of situation before. I'm sure that all the information that I input is correct and real. I don't know why.
iPhone 6, iOS 8.1.3