Sony Ericsson Xperia X10 :: Switching Service Provider Applications?

I purchased an unlocked new Sony Xperia X10 from overseas because I was told it wasn't going to be released in the US. I had been waiting for the release since I had heard about the production of the phone and so I didn't care so much about the price. However, I recently went to an AT&T store and inadvertently saw my phone there and almost punched the first AT&T rep I saw for lying to me. I remained calm and asked if it was possible to get the AT&T software on my phone instead of the Telstra software applications that are non-functional and cannot be removed. They told me, "no, we dont do that, ask sony." Please, someone tell me I can somehow load the AT&T software to my phone, so I can use the applications that came with the phone, like MySync, Downloads, PlayNow, etc.. I spent so much money on this phone, and now it's available through AT&T for $150 with a 2 year contract; I wouldn't feel as terrible if mine could at least DO everything the AT&T one could.