I assume you're talking about SMS 2FA code. TOTP doesn't require any networking - it's just an HMAC of the current time using a preshared key. Whether or not SM

I assume you're talking about SMS 2FA code. TOTP doesn't require any networking - it's just an HMAC of the current time using a preshared key. Whether or not SMS 2FA works with a VoIP number is a decision made by the 2FA provider. The most paranoid of them (usually banks IME) will not send 2FA codes to VoIP numbers - they require a for-real cellphone number provided by a cellular provider. There are some VoIP numbers that try to pretend to be this, but none of them are reliable, and AFAIK Whatsapp does not even try.