Callpassword is a service that sends calls instead of sms. The last 4-5 digits of a calling number are the confirmation code. We use 9999 numbers from our DID pool. It is also possible that you generate the code of 4-5 digits and our system makes a call from the matching DID number. The integration is made via API. This method has already proved itself as a reliable one and a lot of large companies integrate it into their services and loyalty systems. The process is simple: the user enters his/her mobile phone number in registration form on your web-site. Our system gets the number and sends the phone call to the user’s mobile phone. Then the user enters 4 last digits of an incoming call number on your registration form (for example, 495 999-1234 – the code is 1234) confirming his/her mobile number.