On my query as to when Volte upgrade is available to my ZE550 KL model,Asus support suggested me to download manually if not updated and on my request sent me following email. Is it worth trying??
Please find The manually update procedure:-
Step 1 - Please visit our official website via computer :https://www.asus.com/in/Phone/ZenFone-2-Laser-ZE550KL/HelpDesk_Download/
Step 2 - There you'll have to select "Android" as OS and then please click on "Firmware".
Step 3 - There you'll have to find Version WW-21.40.1220.1877and download the file via "Global" link, you'll find donwloaded zipped package UL_ASUS.
step 4 - Please connect your phone to computer through USB cable and then transfer the zipped package in root directory of internal storage.
Step 5 - Remove USB cable and then you'll find a notification on phone regarding system update.
Step 6 - As you'll tap on this system update notification, it would require your permission for installing the file, please press OK and phone will start the upgrade process automatically. Please wait while device gets upgraded and then it will reboot by itself.
NOTE :- 1) Please take data backup before proceeding with upgrade process.
2) Please keep your phone charged atleast or more than 30% .
3) Please don't interrupt the process in between.
Welcome to refer Asus support website:http://www.asus.com/support
If you continue to experience issues in the future, please do not hesitate to contact us.