[Verizon Galaxy Note 4 General] mrjoshjohnsmith:
So, I know for sure that it has to be saved someone within the backup file that you can create through android because I backed up the note 4 phone that had advanced calling activated and then did a factory reset and then used odin to install the latest Stock fw file (the one from 2020 that had the better Modem FW) and as soon as I started it up with the sim card the advanced calling was de-activated and could not be re-activated through the normal channel, but then once I restored the android (or google) backup it was automatically re-enabled after the restore was complete. I suspect it is saved someone in the actually IMS settings app (it is actually a samsung app) which I discovered using activity launcher and apk analyzer. I wonder if you could use activity laucher to figure out if your tmobile version note 4 has this system app in it? If it does have this app, I actually figured out that you can unlock this hidden menu without the verizon program on your PC (you dont even need a PC). All you actually have to do is:

Dial ##366633# on the phone then - Select the enable DM Mode on the phone, and then

After This enter main the main IOTHIDDEN MENU using ##433346# then click

- Data (takes you to Data Programming Screen)

- Edit (Data Programming)

- More (takes you to "Others" Screen)

- Click on Global Hidden Menu Selection & Change to Enabled, and boom done your now have an unlocked IMS Service menu and if you can make it here with your t-mobile phone, then you should be able to copy all the values from someone else's tmobile VoLte working Android phone regardless of what T-Mobile tells you!

Just in case anyone is wondering, I actually tried copying the Carrier Services APK and the IMS Settings APK from my android 6.0.1 phone (my daily driver) to one of my other note 4s that I recently rooted (thank you JKRuse for your ridiculously easy rooting instructions for MM) and installed Lineage 18.1 on (thank you very much Ripee For all your hard work there) to see if I could somehow get these system apps to get VoLte working on lineage (I know it was a ridiculous long shot) and NO JOY :(

This was a sad thing indeed because that is the only thing about my old notes here is that I cannot use the Samsung Smart things app to see what is in my family hub refrigerator (when I am out at the Grocery store) and I cannot use the sams club Scan and Go app because both of those apps require android 8.0 and above! And if it wasn't for not being able to get SMS over IP and Voice over IP working on lineage, it would be a perfect operating system for the note 4's! The only downside I could find was that I could not get a stable 4k video (which I never use anyway because it takes way too much sd card space) and the Bluetooth is not stable. But other than that it runs sooo sooo good on the note 4! It is 10 times faster than the Stock fw and then we could use modern apps! Man I wish we could all somehow work together to get VoLte on lineage and fix the Bluetooth and then Bang we have our notes for another 6 or 7 years at least (especially now that I discovered Aliexpress has sellers that are still making Note 4 battery's fresh which means they have not degraded in capacity like all the ones on amazon and ebay). Anyhow good luck!