Is this violating public accomondation codes?

[Cynthia]

Person A, a Chinese citizen in the United States on  F-1 visa, attempted to purchase an AT&T prepaid sim card.
Person B, the salesperson at the AT&T store, refused to sell to person A a prepaid sim card.
Person B cited the reason for refusing service as "the phone was purchased in China".

This happened in New York state around my local community. At first I thought this is a discrimination based on person A's national origin, but I might have touched upon a gray area that whether the phone's origin is an implication of the person's national origin or such implication does not exist.

Me personally think it does, but I want your opinions.

Edit: It's an unlocked phone certified for usage in the USA and there is no observable difference between the same model of the phone purchased in China and USA.

[Cynthia]

Edit: It's a phone purchased in China, not a phone made by a Chinese company. It's the exact same model of the same phone sold in the USA.