Is this w/the VZW Note4 on AT&T?
If so,you may need to set the APN (if possible) to AT&T.
Once done,make sure you tap on the upper r/h corner & select "SAVE" & after exiting that page,tap to select the AT&T APN.
Re-boot the phone & see what happens.
As for exact compatibility,check here:
http://www.willmyphonework.net/
It'll work,but,not as well as an AT&T branded phone.
2G Network:
850MHz/1900MHz
3G Network:
850MHz/1900MHz
4G LTE Network:
Band4-1700MHz