One of the big advantages to jailbreaking has been the ability to enable tethering without carrier support. That doesn’t mean the carrier is unaware of the way the phone is being used. In fact, AT&T has started sending text messages to customers who are tethering without the company’s tethering plan.

The message reads as follows:

“Did you know tethering your Smartphone to a computer requires a tethering plan? Pls call 888-860-6789 for details or visit att.com/dataplans.”

Some customers are also receiving emails about the usage, alerting customers that they will be automatically enrolled in the DataPro 4GB plan if they don’t get in touch with AT&T. From the email:

“If we don’t hear from you, we’ll plan to automatically enroll you into DataPro 4GB after March 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.”

AT&T says the goal is fairness to customers. Yes, they would like to screw all of us equally.

Around the release of iPhone OS 3.0 and the iPhone 3GS, rumors started to fly concerning MMS and tethering, both of which would get 3.0 support. The word was AT&T was unnecessarily delaying MMS, maybe as far as September, and that tethering would run AT&T customers as much as $55/month.

According to AT&T, none of this is true. They recently sent an email to Wired.com to set the record straight. A spokesman for the company has confirmed charges for tethering (booooo!) though he wasn’t willing to mention specific numbers or a live date for the service. As they’ve stated before, the email maintains MMS for “later this summer.”

By the by, the first day of autumn isn’t until September 22, giving plenty of room for “later this summer” and “September” to mean the same thing. As for tethering, we’re probably looking at a $15 upcharge, which is consistent with other tethering/data plans. Seems egregious on top of an unlimited data plan, but I don’t have much use for tethering. My apologies to those of you that do.