[Nexus 6P Q&A, Help & Troubleshooting] carnivalrejectq:
I'm gonna make a post here since NOTHING seems to be working. I'm a T-Mobile customer. Yesterday, I purchased a great condition nexus 6P from someone because my LG G5 is cracked and I was getting tired of it anyway so I opted to just buy a nexus instead of using my insurance on that phone. Everything is all good except for one major issue. VOLTE and WiFi calling just refuse to work with my sim in the Nexus.

I've called T-Mobile twice. I've factory reset from back up and reset settings twice. I've hard reset from stock recovery once. I've wiped network settings and restored default apns. I've manually changed the apns from what I see on Google, reddit and here. I've copied my apns from my LG G5 where VOLTE and wifi calling work perfectly fine. I've cleared cache. I've cleared the cache of the project fi and hangouts apps just in case there's something left over from the previous owner. I've gone into the *#*#4636 menu and tried a bunch of different stuff several times but no matter what I absolutely can not get wifi calling or VOLTE to work with TMobile on my nexus 6P. LTE it's self works perfectly fine for data.

Yes, all settings for wifi calling and enhanced LTE calling and VOLTE are turned on lol. I've tried the trick where you toggle wifi preferred on and off and restart the phone. Nothing happens. I don't even get a wifi calling reg error. It never shows as active in the data toggle in the quick settings are nor the status bar or dialer. It just isn't active. Same for VOLTE. I AM getting band 12. I can see it in the LTE discovery app. VOLTE just isn't working though. Whenever I make a call I can see LTE switching off and it switches to HSPA therefore making calls really difficult in my shoddy signal area at my house which is why I really need it to work.

I'm fairly certain I can root and install a ROM which will fix these problems but I don't own a PC. :(. I thought MAYBE the previous owner had previously had the phone rooted and tinkered with something somewhere that may have messed something up but that doesn't appear to be the case. Bootloader is locked and recovery is stock.

Can anybody help and tell me what in the world is going on here? I don't want to have to sell this nexus and revert back to my cracked screen G5. I would just switch carriers but I still owe money on the G5 so I was just gonna ride it out til I payed it off.

O and one last thing, after scowling google and forums for hours on end yesterday and today I did see one post mentioning something about this stuff being related to IMS provisioning and settings which are tied to a phones IMEI on T-Mobile and not the sim card and how that person simply called T-Mobile and got a hold of wifi calling technical support who was clueless but created a ticket for him and within 72 hours the issue was resolved. OK well I did the same exact thing and they refuse to create a ticket for me because it's not a T-Mobile phone and because according to them they are not allowed to create a ticket because wifi calling works fine in my G5 and therefore it's the phone and not them or their network lol. What a crock. I'm willing to bet if I put the sim in another unlocked phone with 7.1.1 and wifi calling fully available that it isn't going to work either. There's some sort of communication error going on between the sim being in this phone and their network it appears.

Check these screenshots out. T-Mobile is clueless

http://imgur.com/5MuO34s

http://imgur.com/XVd8CdA

http://imgur.com/uUGN3ae

http://imgur.com/cfYxfqh