i-phone activation

I bought an iPhone 6s in China and used a Chinese carrier, China Mobile. I just moved back to the US and want to use my iPhone here. I put a new SIM card in (using Straight talk) but my phone says that my iPhone is not activated. Straight talk comes with SIM cards for Verizon, All-tell and T-Mobile and none of the SIM cards worked. In the upper left corner of the screen it just says “TFW”

What can I do?