> eg. customer has a static phone number in one country that they have continuous SMS access to, customer wants to install your extra app, whatever GitHub uses

> eg. customer has a static phone number in one country that they have continuous SMS access to, customer wants to install your extra app, whatever GitHub uses TOTP which does not require SMS, can be used with dozens of apps (because it's a protocol), and can be easily transfered using QR codes or seeds.