A bunch of crybabies. First they want you to not include firmware files for newer ROMs, and then they come over to complain about malfunctions caused by outdated firmware (like the call feature). Seriously, people, you should have stayed on stable MIUI 9, that could avoid all this headache.
Im like 100% sure that the people who compalined about calls and such, installed the rom wrong or flashed it over their fake 9.6.4.0 global rom because they have no idea what they are doing. because of that their firmware is bad and they complain to you about it. if you install it right like I did you have literlly 0 problems! not in calls and not in anywhere else... if you added the firmware-update because of these people and not because of a real problem, you literlly tried to help someone that did a bad installation / installed a 3rd party zip (like root), and when they do that you dont wanna help them, so why helping in this situation when they come to you after flashing your rom wrong? those who installed the rom right had no issues with the calls on 8.8.23 or any other version.
You should have atleast told us about the fact that you added this firmware-update becasue now people got anti-rollback on a rom that wasnt supposed to have it just because of people who installed their rom wrong...
You tried doing something good for the people who had problems but you havent looked forward to how and what they installed and you didnt think about those who didnt want anti-rollback and got for no reason...
I just hope that when you add the firmware-update to Redmi Note 5, Mi 6x and Redmi 6 Pro ; you will tell them on the changelog that you are going to add anti-rollback to them
Thanks for trying to help and have a good day!