help of telephone manager get country code and flag and also popup for all country code and search functionality and also add StickyHeaders Like Ios above every new starting letter. list of header refrence https://github.com/emilsjolander/StickyListHeaders
and for listview SectionIndexer use Refrence http://androidopentutorials.com/android-listview-fastscroll/
tou can also refer https://android.jlelse.eu/fast-scrolling-with-recyclerview-2b89d4574688