// Android 1.6 and earlier (backwards compatible for Android 2.0+)
Uri uri = Uri.withAppendedPath(Contacts.Phones.CONTENT_FILTER_URL, Uri.encode(phoneNumber));
// Android 2.0 and later
Uri uri = Uri.withAppendedPath(ContactsContract.PhoneLookup.CONTENT_FILTER_URI, Uri.encode(phoneNumber));
// Query the filter URI
String[] projection = new String[]{ PhoneLookup.DISPLAY_NAME, ...
Cursor cursor = context.getContentResolver().resolver.query(uri, projection, ...