Samsung S7 SM-G930FD (baseband version G930FXXU1BPJG) unlocked

Need some guidance. Called Samsung (US) but they will not provide support because my phone is an international version...anyways.

I have a Samsung S7 SM-G930FD (baseband version G930FXXU1BPJG) unblocked. My service is US based (ting.com). I have two SIM cards installed. GSM.

SIM1: voice/data/text (LTE/3G/2G)
SIM2: voice only (2G)

The phone does not have WiFi Calling option to turn on. My provider provides WiFi Calling.

I want to be able to have WiFi Calling option on my phone so that I can increase my phone coverage on wifi in my office...as the GSM signal is weak.

Thank you in advance for any guidance!