WhatsApp: when you install it, the verification is done with a six-digit code sent to the phone via SMS. However, WhatsApp seems to be working on another method for account verification.
According to the news of the WABetaInfo site, the account verification method by leaving a call to the phone in the Android application of WhatsApp is being tested. For this, users need to allow the method in question. Users will not be required to answer the call from WhatsApp.
Even if this feature is made available, it seems to be limited to Android. iOS does not allow apps to read call history. The news of the WABetaInfo site also includes the information that the application will access the call history to verify the last record and will not use the data elsewhere.
Instagram, which is also owned by Facebook, is testing sending verification codes from WhatsApp instead of SMS.
It can be said that recent times have been active for WhatsApp. The future of multi-account support for the service was also confirmed by Facebook CEO Mark Zuckerberg a while ago.