Wow you got lucky TWICE: 1) VZW didn't auto switch you to a 2GB line when you called about activation and 2) that the apple store was able to update the activation date for you.
Similar to Campguy I got my iPhone6+ early via ship to home last Friday (originally scheduled Oct 14-21) and couldn't activate it. I worked through Apple Support for 6 hours over the weekend including doing an iTunes restore but no luck. Finally decided if I could get lucky with Verizon asking for a tier 2 tech but they added the account as a 2GB line. Even then the phone still wouldn't activate but I immediately asked to cancel it and return the phone. Called apple to initiate a return on Saturday and said I wanted to return in store on Monday and the support woman said sure sounds good, I'll send you a return shipping label in case you change your mind on going to the store. Turns out that was a bad idea. Found out in the store on Monday that her ordering the return label blocked me from doing a store return. Called Apple support to override which they did (force canceled the return label) but still no dice after waiting 10 minutes and trying multiple times. Decided to try again today, still not working in their system. Was on with apple support another hour while in store, going to try one more time tomorrow with the help of their ISNT team ("there super special hacker team") to fix the system. Then I will make sure to call VZW to get someone on the line to talk to the store manager to confirm the return and wait the 72 hours to try and do a store-pickup on Monday.
Note to anyone wanting to return an apple.com order DO NOT REQUEST A SHIPPING LABEL, just take it into the store and they should be able to help you.
I think key is to have same messaging plan on the new line which is existing ony our current calling plan. The activation date needs to set correctly. Problem is Apple shows ship date couple of weeks in future but they ship in 2 weeks so first place is to go to Apple Store and get activation request sent from Apple to Verizon, wait for 24 hours and then directly try activating phone. I think this would work without having to call Verizon. I called them for number porting and not even once they got clue about UDP on new line. If Apple sends activation request then line would get automatically added with UDP on it to your account. Verizon Credit department simply performed this step manually (pushing line on my account).