Yes that is a very good suggestion. XDA is the authority when it come to android development. Be aware that the n910v (Verison Note 4) has a locked bootloader. Before you flash anything it needs to be unlocked first or you will brick your phone. Secondly, you will need to go to settings, about device and tap build number 5 to 7 times in order to reveal "developer options". Go bact to main settings and you will now see developer options. Click it and go to usb debuging and enable it. Make sure you read XDA for specific details about your Note 4. You will also need an official firmware specific to your phone. Search the form and theres a good chance you will find an official firmware specific to your device. Use an Md5 to validate your download.
If you purchase your Note 4 on Ebay, it is possible that the phone you purchased was an Sm-n910v in large print and in the description the hardware was from another carrier.
Also it may be that Verison has lock out the apns settings on the updated firmware. Best check xda to be certain.
If you decide to root, the most important thing I can tell you is to install a custom recovery like TWRP. I can honestly tell you that the kost important thing when rooting it make a backup immediately, check all partitions before backing up. Furthermore, TWRP will prompt you to install root. DO NOT LET TWRP INSTALL THE SU-BINARIES, YOU HAVE BE WARNED. Good luck