T-Mobile doesn't do the updates (nor does any carrier) they are all done by the manufacturers in this case Samsung. I have attached the press release from Samsung regarding Nougat and if you look down in the fine print the Note 4 is/was not on their list of devices they were going to update to Nougat. :-(
Well... sigh.... based on the comments and links, we can lose all hope of getting back our Note 4 with an ever decent update... I wouldn't mind an update as long as my Note 4 would work for days in a row instead of 4 to 10 reboots everyday... sometimes it is so bad that I have to remove the battery... and sometimes an entire day goes by flawlessly.
I guess we will be left to root and do custom firmware ...