Retrieve data from Field API programmatically
Use Field data extraction API module to accomplish your job of field data extraction.

As per the documentation, you have to write this in yourmodule

  $phonenumbers = field_extract_values('node', $node, 'phone_number');

  $result = someCustomFunction($phonenumbers);

  function someCustomFunction($user_phonenumbers){

   // Do something here and return value

   }