Starting Sunday, all new customers to AT&T will have a new pricing structure for their text-messaging plans: unlimited or pay-per-text.

Starting August 21, we’re streamlining our text messaging plans for new customers and will offer an unlimited plan for individuals for $20 per month and an unlimited plan for families of up to five lines for $30 per month. The vast majority of our messaging customers prefer unlimited plans and with text messaging growth stronger than ever, that number continues to climb among new customers. Existing customers don’t have to change any messaging plan they have today, even when changing handsets.

The cost will still be $20 for the unlimited plan (and $30 for family) just like it is but that’s the only text messaging plan that will be available. If you don’t go with a plan then you’ll pay $0.20/SMS and $0.30/MMS.

This is a smart move by AT&T. If you send more than 3 text messages a day then it’s cheaper to get the unlimited plan. The vast majority of new customers will go with the unlimited plan. Especially any and all new customers who may be switching to AT&T later this fall due to a certain new phone and a certain new OS.

With the previous plan option of $10/1,000 you could send 32 text messages a day before the unlimited plan became cheaper. And with iMessage rolling out this fall it means new (and current customers) on iPhones who likely would have gone with the $10/1,000 plan will instead go for the $20 unlimited plan.

But I think it’s silly to say that this move is solely in response to iMessage. AT&T has nearly 100 million wireless subscribers. And the total install base of American smartphone users are still outnumbered by non-smartphone users 2 to 1. Put another way: there are a lot of AT&T customers who don’t use an iPhone.

On a personal note, Anna and I will be sticking with our unlimited family messaging plan. At $0.20 per text we could only send 150 text messages per month before the $30 plan got cheaper. We each send close to 150 texts in just one week. And, except for one cousin on my mom’s side, not a single person our entire family owns an iPhone. Thus, iMessage won’t be incredibly helpful to us.

AT&T’s New Text Messaging Pricing