I bought my phone from best buy and paid in full in September. It was guaranteed that it can be work in China. However, when I come back to china and change the Lycambile card which I used to activate my iphone 7 for other chinese SIM card, it can't be work and prompt me for invalid SIM card. The best buy costomer service told me that I need to contact the carrier to unlocked, and I found the carrier showed in my phone is T-mobile, that's why I am here. So, please held me and e-mail to firstname.lastname@example.org. Thanks.
*edited personal information - Marissa