A Fraud charge on my ATT Reward card/200 dollar reward Card only has 50 dollar balance

I have a $200 reward card issued by AT&T. When I tried to make a purchase of $130 dollar it got declined. I contacted ATT reward center and they told me this card only has $50 balance. There was a $150 charge from merchandise 'US International' and thus I only have $50 balance. I have no idea what's that merchandise is. ATT claims they knew nothing about this merchandise and there is nothing they can do. I felt like it's either a scam charge or ATT used it internally. Has anyone had similar experience?