OK so after I had to do the below hack several times, it failed - for good. It would not revert back to StraightTalk. It just said Verizon no matter how many times I repeated the hack below over the course of a couple weeks and any other method I could find on the internet. I stopped short of re-purchasing a gevey chip or a new staight talk chip.
Gave up - went to the no contract, $60 a month Verizon plan.
If you want to give it a try, you may have better luck, continue on...
Here's what you can do if you wanna keep your phone but get the (currently in 2013) $45 unlimited everything (the $30 plan won't work with this method) of AT&T and Walmart's Straight Talk plan. Walmart and AT&T teamed up for that. Kinda cool.
You can spend days googling this to understand what it is exactly that you're doing and since you have free time you might wanna do that. Its kinda interesting really, but not necessary.
1. The little tool to open your sim card slot on the side of your iphone - around $1.50 on Amazon UPDATE: Embarrassed to realize you can just use a paperclip.
2. The Straight Talk kit you can get online or at any Walmart - First months $45 fee and the AT&T micro sim card. Total $65
3. The gevey ultra sim card. You can go to gevey.com but I got mine at Amazon for half the price, about $17
Here is a lovely How-To (with pictures!). If you have NO idea what you're doing, pictures are brilliant:
GETTER DONE (AGAIN!):
This is what I did to get mine to work when it once again went back to Verizon. The above worked the first time but I had to do it a multitude of times the next. And yes, for some unknown reason my phone reverted back to Verizon 3 times. Utterly annoying. Heavy sigh.
Reboot with unlock chip in (the gevey white chip)
Select verizon when the screen asks for your carrier
Immediately (maybe 3-5 seconds or so) take out and replace w/ gevey + straight talk chip combo
Click accept when the screen pops up to tell you your phone has been unlocked
Reboot phone > its gonna say Verizon
Dial 1-888-634-9474 once connected, end call
The go to SETTINGS > airplane mode on - wait a few seconds - then switch airplane mode off again
It should now read HOME (which is the straight talk network name)
Set APN: Settings > General > Network > Cellular Data Network
If you don't have the Cellular Data Tab:
1) Cydia > Manage > Storage > Sources
2) Add source iHacks Repo: http://ihacksrepo.com
3) Then add TetherMe APN Editing
It should now appear in your Settings. (I didn't need to reboot).