I did it to my account, but it took 8 months of fighting with NA and JP support, with lots of Google Translate, to get it done in 2011. They said it was a one-time thing, and I'd need to make a new account if I moved between regions again.

JP and NA support do not talk to each other, and NA support cannot see anything in a JP account to assist.

I still have a JP PlayOnline Account, so I've had to buy Adoulin from Japan, but I can now pay my fee with American payment options.