I've read a few others having this issue. I also have this issue. I did a reset of all settings and now it shows a spinning wheel for a while, then "Set Up Personal Hotspot" and prompts to call Verizon. (are you Verizon as well?) I spent hours with a rep troubleshooting with no fix. I've completely restored the phone, set it up as new (no backup) - nothing works. Verizon claims all is set up on their end, they tried resetting things to no avail.
I also don't have the VoLTE feature that is supposed to be behind the Enable LTE option. (its just a simple on off switch, where it should lead to another menu area)
I suspect bad hardware but am curious if others have run into this and if anyone has found a fix.
My wife's new Verizon iPhone 6 works just fine.
iPhone 6 128gb Verizon, iOS 8, switched over from AT&T so had my number ported.