[Q] please help with advice on tmobile sm900t topic

bought a tmobile sm-n900t note 3 for a Christmas present and come to find out there is money owed on it, its NOT STOLEN!!!. I have no tmobile sim card either. is there a sim UNLOCK program I can use or can I do a phone unlock or use a root program? if this helps it runs android version 4.4.2...... build number??? n900tuvucnb4....I didn't want to use tmobile for service as I have everyone on h20 service. but when I took it in the guy said it had to have a sim unlock code hence the reasons I ask about programs. thank you for your help....happy new year!!!