The terms of what that $100 went to were updated last month...

https://smartphones.gadgethacks.com/news/trump-mobile-t1-sma...

    The terms, updated April 6, state that the deposit is not a binding sales contract. It provides only a "conditional opportunity" to purchase the phone if Trump Mobile eventually chooses to sell it, with all discretion resting with the company. The company "does not guarantee that a Device will be produced or made available for purchase," The Verge and IBTimes UK reported.

So yea... a $100 voucher for a conditional opportunity to purchase one if Trump Mobile ever decides to sell one.

So just a scam.