Yes you can sell the share if you own it, but you won't be getting $43 for free. Assume you get 1 share of T-mobile stock currently valued at $43.11 and you want to sell the stock.

Since you did not hold this stock for more than 1 year, you will be taxed at regular income so if we assume a 30% tax, then you will be left with $30.18.

[1] As the nandhp points out below, T-Mobile is issuing these shares exclusively through LOYAL3 and selling your share within 1 year will be fee-free.