Just got an email this morning about this offer. From now until 04/17, you get an extra $225 off for each new line of service activated with T-Mobile when you are porting your phone number over from another carrier. This offer seems to be only available when you call the phone number 844 786 2964 and mention the promo code STUDENT01. Says it can't be redeemed at the retail store or via the regular T-Mobile number.
This is where the savings come from:
Get a $200 T-Mobile Bill Credit for each mobile number you port and switch from the other guys to T-Mobile ONE or Simple Choice ** [t-mobile.com]
Save $25 per line:
Waived SIM activation fee
I also shared a screenshot of what I received via email.