I just flashed the latest stable official Lineage ROM for S7 Duos (SM-G930FD), using the following process
1.Boot to TWRP recovery
2.Wipe everything except external SD (contains zips)
3. Add following to zip queue, flash, reboot.
4. Everything is working as expected, EXCEPT I'm unable to make/receive calls or send SMS.
The SIM is being detected with correct network, I can receive SMS and LTE data is working so it looks to be a software/config issue but I'm out of ideas, so would appreciate any pointers on what to check.