Welcome to Android Central! Do you mean that they won't carrier unlock the phone according to their policies? https://www.sprint.com/en/legal/legal-regulatory-and-consumer-resources?ECID=vanity:legal. Or that the phone won't work properly on other networks due to its inherent band compatibility? From what I can tell, the Sprint Note5 wouldn't be compatible with T-Mobile's LTE spectrum, since the phone uses LTE Bands 25, 26, and 41, and T-Mobile uses 2, 4, and 12. That's not something that Sprint can change for you.