Updated 2/7/12: This morning, Straight Talk began selling SIM cards and service without the need for a hardware purchase. It is now easier than ever to use Straight Talk’s popular $45 unlimited talk, text and data pre-paid plan with your AT&T or unlocked iPhone. For details, see this post.

What would you say to an unlimited plan for $45 per month? With no contracts? Running on the same nationwide AT&T network? Do I have your attention yet? Introducing Straight Talk’s unlimited plan:

That’s a savings of over $70 per month from AT&T’s postpaid offerings, and you’ll be free of any contracts. There was little doubt that it was possible, but I can now confirm that there are no issues using the new iPhone 4S with the $45 unlimited everything (talk, text, data) Straight Talk prepaid plan. This doozie of a deal has been around for quite a while, but it’s worth a quick review for those who haven’t heard about it before.

Here’s what you’ll need:

• Any iPhone that works with AT&T. It doesn’t even have to be unlocked, because we’ll be using Straight Talk’s AT&T-powered MVNO.
• A Straight Talk smartphone. I recommend the Nokia E71, because it has been widely tested and confirmed to contain the correct TF64PSIMC4 SIM for use with the AT&T MVNO. Those in a rush can pay a premium for the smartphones available at your local Walmart, or you can order a refurbished E71 from their website for $99 $49 with free shipping.

The procedure is quite straightforward:

• Activate your Straight Talk smartphone from their website with the included SIM.
• Verify that your Straight Talk smartphone can make an outgoing call.
• If you’re using the iPhone 4 or 4S, take our that SIM and punch it down to size. (If you don’t already have one, I have had good luck with this inexpensive Noosy micro SIM cutter.)
• Pop that slimmed-down SIM into your iPhone. It will take a moment to acquire service, after which you should see “HOME” displayed in the carrier field.
• To enable Internet access, email yourself this configuration file and open it. (If you don’t trust me, go to unlockit.co.nz or help.benm.at and generate your own configuration file using att.mvno as the APN.)
• Done. Enjoy the same AT&T service for a new, low price.

Not too difficult, right? As always, there are a few other caveats worth mentioning:

• If you’re going to port your number from your current carrier, do so when you first activate the phone. You will not be able to do so after you’ve activated the SIM.
• If you want to use “classic” MMS with this plan, you’ll need to jailbreak your phone. I didn’t bother, because I only send pictures via iMessage or email.
• Don’t push it with the “unlimited” data consumption. I’m certain they monitor your bandwidth, and I guarantee there’s some fine print somewhere that says that unlimited is actually quasi-limited. Just use your phone as a smartphone, and don’t go nuts with tethering and BitTorrent, and you should be fine.
• I know you’re tempted to unload that unused Straight Talk smartphone on eBay or Craigslist. Resist the temptation. If you ever need to deal with Straight Talk support, they may require you to use their handset to duplicate the issue. The cost of the phone is a small price to pay, and it will pay for itself in just a few months of savings.

All things considered, it’s an excellent deal.

Is anyone else using Straight Talk with their iPhone? What are your thoughts?