This is exactly why I don't plan on jailbreaking my iPhone. As much as I miss custom themes, I can't imagine being phone-less like that - not to mention that Apple has been known to refuse service on JB'd phones in the States.-snip-
Anyway, they told me the same thing when I tried to get my first iPhone replaced at the Genius Bar in Shibuya. My response was 'you have got to be ****ing joking' or something along those lines, at which point they arranged to have me pick up a replacement at the Omotesando Softbank shop.