My unlocked brand new IPHONE locked by internet lock - How to unlock my iphone

I bought this device on 03/21/2019 and the clerk told me this is a unlocked version device. Later, I used a T-mobile sim card to active the IPHONE. This SIM card purchased in China before I visit USA. Everything is ok.

After I came back to China and tried to use local sim card to active the Iphone. But Iphone remind me this sim card is invalid. I inquired this device with serial number in appler service ceter online. I was informed this device is locked with T-mobile.

Here is the pic1 The receipt of iphone

Pic2 inquiry result