It appears that some US iPhone owners who are looking to upgrade to the recently announced 16GB version are being forced to sign extended 2 year contracts as part of the upgrade process.

Posted on the official Apple discussion forum, one user writes:

“I just came from the ATT store where I fully intended to buy the new 16GB iPhone (I have had an 8GB iPhone since day one and have loved it, though I think ATT isn’t the best service provider). However, when the sales agent explained that I would have to re-up for another 2-year committment from ATT, I decided not to buy the new phone — at least at this time. The sales agent said that my original 2-year plan would end the day I activated the new phone and a new 2-year plan would be initiated!”

It appears that some iPhone owners are able to upgrade with no need for an extended contract as this user writes:

“I went down to AT&T store and bought an 16GB iPhone. To activate it, I had to choose that I was replacing a current phone with this iPhone. I kept the sim in the iPhone that the new 16GB phone came with. Activation was fast and easy and I am still where I was in my contract as I was yesterday, 6 months into the 2 years. The iPhone would not activate with the old sim card in the phone until I put the sim the new phone came with back into the new phone.”

[via Apple Discussion Boards]