Why one of my old contact show as unknown?

[Android Central Question]

I had this contract for 7 years in my phone. Thday is the only one shows like this.

 

[B. Diddy]

Welcome to Android Central! Is it showing up as unknown only when they call in? Is the number they're calling from exactly the same as what's listed in your Contacts app? If one of them has a country code and the other doesn't, the phone might not recognize them as the same.