I'm building an app where I need to verify if a mobile no. exists in a mobile device just like banking applications. Can anyone help me?
If its an android application, there is something called as content provider/content resolver (a component providing information of one application to another, ex: for the first time when we install Whatsapp, it will ask us, if it can use contact information from our contacts application). Using this, you can access all the contacts and check if a number exists (Need to add permissions in manifest file)
While there is no database you could query there is always the option to send an SMS with a code the customer has to provide.
Mario Giambanco
Director of User Experience Development
Marco Alka is on the right track.
Have the user enter in their phone #
Use a service like twilio.com - send that phone # an SMS with a code.
User enters that code into the app - phone # verified. Lots of companies do it like this - google, apple, etc...