Despite the fact that AT&T officially jumped on board the iPhone tethering bandwagon last year with the release of iOS 4 -- a full year after Apple first added the capability with iOS 3! -- many jailbreak users have been content to use the $20 MyWi app with their unlimited data plans. Now those days may be coming to an end.

Cult of Mac is reporting that a number of jailbroken iPhone users have started to receive an ominous free text message from AT&T, not so subtly hinting that said user should jump on board the official DataPro tethering package and curtail their use of MyWi, a popular $20 Cydia app which enable tethering on any jailbroken device.

“Did you know tethering your Smartphone to a computer requires a tethering plan?” the free text message from AT&T asks, providing details for the user to contact the carrier to get official.

While the text message itself isn’t very threatening, at least one user had that communique followed up with a much more extensive e-mail from AT&T which clearly spells out, “Our records show that you use this capability, but are not subscribed to our tethering plan.” The e-mail states that if the user discontinues their illicit tethering, they can keep their grandfathered unlimited data package -- or the carrier will “automatically enroll” them in the official DataPro 4GB package after March 27.

AT&T has yet to provide a comment on the subject, but it sounds like the carrier may be starting an initiative to end the original iPhone $30 per month unlimited data plan by any means necessary -- particularly now that they have a more potentially lucrative capped data plan for the handset which nets them extra fees for each gigabyte used after the initial 4GB pool.

The full AT&T e-mail follows!

Dear [Customer],

We’ve noticed your service plan may need updating.

Many AT&T customers use their smartphones as a broadband connection for other devices, like laptops, netbooks or other smartphones– a practice commonly known as tethering. Tethering can be an efficient way for our customers to enjoy the benefits of AT&T’s mobile broadband network and use more than one device to stay in touch with important people and information. To take advantage of this feature, we require that in addition to a data plan, you also have a tethering plan.

Our records show that you use this capability, but are not subscribed to our tethering plan.

If you would like to continue tethering, please log into your account online at Cell Phones and Cell Phone Plans – Wireless from AT&T, or call us at 1-888-860-6789 Monday – Friday, 7 a.m. – 9 p.m. CST or Saturday, 8 a.m. – 7 p.m. CST, by March 27, 2011 to sign up for DataPro 4GB for Smartphone Tethering.

Here are details on the plan:

DataPro 4GB for Smartphone Tethering
•    $45 per month (this gives you 4GB in total, combining both your smartphone data plan for $25 and the tethering feature, $20)
•    $10 per each additional GB thereafter, added automatically as needed
•    Mobile Hotspot capabilities are included for compatible Smartphones

If we don’t hear from you, we’ll plan to automatically enroll you into DataPro 4GB afterMarch 27, 2011. The new plan -- whether you sign up on your own or we automatically enroll you -- will replace your current smartphone data plan, including if you are on an unlimited data plan.

If you discontinue tethering, no changes to your current plan will be required.

It’s easy to track your usage throughout the month so there are no bill surprises. For example, we send you free text messages when you reach 65, 90, and 100 percent of your plan’s threshold. If you would like to monitor your account more closely, go towww.att.com/dataplans to learn about other ways to track your data usage.

As a reminder, our smartphone data plans also include unlimited usage of Wi-Fi at no additional charge. AT&T smartphone customers can use Wi-Fi at home or on-the-go at any one of our more than 23,000 U.S. hotspots already included in your data plan.

Thank you for bringing your account up to date. We appreciate the opportunity to continue to serve your mobile broadband needs.

Sincerely,

AT&T

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(Image courtesy of Cult of Mac)