By Sam Oliver

Published: 01:50 PM EST (10:50 AM PST)

Ahead of Apple's anticipated next-generation iPhone announcement, AT&T has begun modifying some customers' upgrade dates, shortening them in some cases by months to allow customers to buy a new, subsidized handset in June.

This week, a reader contacted MobileCrunch to say that his upgrade date was moved from Nov. 21, 2010, to June 21, 2010. The customer said they bought an iPhone 3GS in 2009 on the device's launch day.

"As a valued AT&T customer, we can offer you a discounted iPhone upgrade at a higher price, along with a 2-year commitment and an $18 upgrade fee," the customer's account profile reads. "Please proceed with the online upgrade process for pricing details. You may qualify for a full discount on a standard iPhone upgrade on 6/21/2010."

The same changes have appeared for other customers, but not all. AT&T has revealed in the past that generally speaking, the more a customer spends with AT&T, the quicker they become eligible for a price break on a new device. For example, iPhone customers who spend more than $99-a-month per line are generally eligible for an upgrade between 12 and 18 months into their contract.

The revised dates will likely pave the way for AT&T to offer some customers reduced prices on Apple's latest iPhone, expected to be announced in June. It's the same approach AT&T has taken in the past. Last year, the wireless carrier offered early iPhone 3G adopters the opportunity to purchase an iPhone 3GS as the same $199 and $299 price points as new customers.



In years past, Apple has introduced its annual iPhone upgrade at the Worldwide Developers Conference. This year, WWDC 2010 will be held June 7 through June 11 at San Francisco's Moscone West. Tickets for the event sold out just eight days after Apple announced the dates.

In April, one rumor suggested Apple could sell the next-generation iPhone as soon as it is announced on June 7. That approach would be a change from years prior, when a new handset was announced a few weeks before its sale date. AT&T has also blacked out the month of June for its employees, preventing them from taking vacation days.