Did you buy a shiny new iPhone 6 from AT&T Wireless? You might want to check your next monthly bill for an increased charge.

Some AT&T customers upgrading to the iPhone 6 received a surprising text alert this morning saying the carrier has hiked the monthly “smartphone access charge” to $40 for anyone renewing a two-year Mobile Share Value plan agreement. Naturally, the carrier waited until it was swamped with an unprecedented amount of iPhone 6 pre-orders before telling customers they’d be paying an extra $600 over two years — nearly enough to buy an unlocked iPhone 6 outright.

AT&T says certain users are “no longer eligible for the discounted pricing” that reduced the $40 monthly access charge down to $15 or $25, depending upon when they signed up.

The increased charge applies to people who buy a discounted phone under the traditional pricing structure, where the carrier recoups the purchase price over the course of the two-year contract. Those who buy a new phone at full price or opt into AT&T Next — which charges subscribers an extra monthly fee but lets them upgrade to a new device each year — can still get the discounted access charge.

Customers who noticed the increased fee are not happy, as can be seen by angry reactions on Twitter:

@cultofmac Yep! I did. Called them and they seemed to not give a shit. Told me the only way to keep my plan was to pay more on NEXT. — Stefanie Valle (@stef_valle) September 18, 2014

During previous iPhone launches, when AT&T customers renewed a two-year agreement they received the iPhone at a discounted price, with the carrier recouping the costs over the course of the contract. Now AT&T charges users between $15 and $25 extra per month as part of the access fee if they choose a new two-year plan. That’s on top of the $40 upgrade fee you also pay when you buy your iPhone 6.

It’s all part of the changing landscape of the mobile industry, where T-Mobile’s innovative pricing is shaking things up and forcing bigger players like AT&T and Verizon Wireless to evolve. AT&T appears to be using the popularity of the iPhone to help push customers toward its AT&T Next offering.

@ATTCustomerCare so buy the phone retail price or pay you monthly for the phone. Still sounds like customer loses. So it’s @TMobile for me — cr0ssed (@cr0ssed) September 18, 2014

An AT&T spokesman said the upset customers likely had been on a Mobile Share Value plan with a phone that was out of contract, or were using AT&T Next for their previous phone, or chose to pay full price for the their previous phone — all scenarios in which they would have been paying the discounted access charge.

“In any of those cases, if they just chose to get a new phone under contract, they would be seeing the higher access charge,” said AT&T rep Seth Bloom in an email to Cult of Mac. “Put another way, the only customers who would see the higher access charges are those on two-year contracts and who are getting a subsidy from us.”

AT&T apparently failed to mention the change to customers until pre-orders were already on the way, and the carrier’s Mobile Share Value webpage obfuscates the details by listing pricing terms prior to 2/2/14 and 3/9/14.

Meanwhile, the AT&T customer support account on Twitter is directing angry customers to a notice on their site that offers “important information about your recent device upgrade.”

It basically says, “No no no. We’re not charging you extra now. We’re just removing a $15 discount from the $40 monthly charge this year. Even though we touted that access charge as a flat $25 fee the last few years.”

Here’s the explanation from the website:

Thanks for upgrading to a new smartphone and selecting the 2-year wireless service agreement option, which does not take advantage of our best-ever pricing with Mobile Share Value. Upgrading your new device on a 2-year wireless agreement means you are no longer eligible for your Mobile Share Value monthly smartphone access charge discount. This discount is $15 off the $40 per month 2-year agreement rate access charge for Mobile Share Value plans that include less than 10GB of data.

Yikes. So now AT&T is going to punish you if you want to upgrade your contract every two years like you always did. But if you do want to get your discount back, you totally can — AT&T conveniently left a ransom note: