Which CSC should I flash to enable VoLTE on T-Mobile USA (SM-G935FD)

Hello there,

I am looking to flash a custom rom to my SM-G935FD (International Dual-Sim EXYNOS variant). I have heard that there is a hybrid "TekHD" CSC which enables T-Mobile VoLTE/wifi-calling on SM-G935FD. Here are my questions:

1. where can i find this elusive hybrid TekHD CSC?
2. if not the TekHD, which CSC should I flash to enable VoLTE and wifi-calling on my SM-G935FD?

Regards