From MediaTek: "MediaTek enables dual SIM 4G LTE voice and video for Indian smartphone users"

Callers in India are celebrating one of MediaTek’s most far-reaching advances that often flies under the radar: enabling dual 4G LTE on both its SIM connections in all its latest Helio chipsets. Phone makers in India are hurrying to embrace this ability to offer voice (VoLTE) or even video over LTE (ViLTE), enriching family and business life and expanding communication choices as never before. Dual 4G SIM gives you consistent, ultra-high-quality voice and face-to-face video performance regardless of which SIM data connection you choose.

MediaTek's leadership in DSDS technology enabled it to (again) be the first to enable this exciting new capability when it launched the Dual 4G SIM Dual Standby (DSDS) feature in 2017, and it has been enabling ever more chispets ever since. Zenfone Max Pro M1 was one of the first handsets to reach India, with more following this year. 

Indian service provider Reliance Jio is one of the largest carriers offering data-only 4G, so users wishing to make calls need a VoLTE-capable smartphone; now MediaTek offers Indian users the ability to call on either SIM, giving them a needed choice. Of course, customers who pay only for data are thrilled, with voice calls that are local, national or roaming all costing the same.