HI, I am having the same problem. I would like to switch store and haven't been able to spend the last 0.70$ credit I have in my account. I am switching store because I moved to another country (Bangladesh) and I read I could do this as soon as I have no balance on my account. I don't have a credit card with US billing address to add credit. As, I am in Bangladesh now and can't buy iTunes card here.
I have tried to use my AMX card issued from Bangladesh. While updating the billing info I failed to attach the card in the billing information. Every time the billing was successful but, iTune store shows that the payment declined where as I got the text from bank the transaction was successful.
I'd like keeping my present account because, there are several products registered against this iTune account. Please let me know, how can I solve the problem