Mobile verification can be done via missed call to the given number

This is how you go about doing it

• If you are building an App that requires a mobile number based authentication, take the user’s phone number as input
• place a call from your server to the number and stop after one ring
• Your app will intercept the call and see the callerID to verify it is our call
• Truecaller has added missed call as a verification mechanism in their API using a similar mechanism