It looks like AT&T is continuing the crackdown on unofficial tethering as readers have reported another round of text messages from AT&T this morning:

AT&T Free Msg: We've noticed you're continuing to enjoy the tethering feature with your smartphone service. Remember, you need a tethering plan ($45/mo, incl. 4GB) to use this feature, so we're planning to update your line with the required plan soon. Visit or call 888-860-6789.

Last month AT&T sent out text and email notifications to iPhone users who used MyWi to tether their unlimited data plan. AT&T threatened to switch their plan over to the Data Pro 4GB tethering plan unless they called in, and some users reported success in keeping their unlimited plan when claiming they used large amounts of data from apps like Netflix and Pandora and weren't using the tethering feature.

It appears AT&T is pretty serious about putting a stop to unofficial tethering at this point and won't be letting up anytime soon. In addition, it was previously speculated that one of the tracking methods they used was simply targeting high data users (10GB seemed to be the threshold), but some users receiving the message have used tethering extremely sparingly, keeping their monthly data usage well below 10GB since the original message was sent last month.

Have you seen any new messages from AT&T regarding unofficial tethering? And more interestingly, do you think it's fair for AT&T to strip users of their grandfathered unlimited data plans for using the data they've already paid for in an "unofficial" way? Let us know in the comments!