[downvote_korok]

off-topic:- We use only SMS. Our family owns a grocery chain in NorthEast India, Last I built a ecommerce app where only login method is through SMS (OTP). Initially we thought this will be very bad. But now we have a significant amount of revenue coming from the app (Native and Web). In india most of the Govt and Private apps use only SMS as login method.

[mnw21cam]

Beware. SMS is not secure.

[ksec]

But it is the only method where people understand and use. And social engineering / account take over from MNO are something that is non-existent in many countries.