You should be able to unlock it after using it for 40 days on T-Mobile although I remember when this came out some people reported that if you got a cool rep on the phone they'd unlock it for you right away, YMMV.
Oneplus 7 Pro 6GB RAM and 128 GB storage is available at $499. Get additional 5% Student discount from Student beans to get it at $474 and use Paypal with Chase credit card to get additional 5% cashback. The final price would be around $450. The one color available is Mirror Grey though.
Or Buy Oneplus 7t at 599$ and get bullet earphones free. Student beans and paypal discount valid on this too.