Question regarding gift cards for Windows Phone

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I'm from Pakistan. Since the store for WP here is limited, I use the Australian region to buy apps on my Windows Phone (when I had a Lumia 920). I have an Australian credit card (my sister's who lives in Australia) setup on my Microsoft account. Unfortunately I will no longer be able to use the card anymore and will need to shift to using a gift card. Currently I have an iPhone, so to switch back to a Windows Phone, I need to confirm something.

Can I buy a Microsoft gift card from Best Buy: Experience the Ultimate Showroom or Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more and redeem it in my Australian account, whilst physically sitting in Pakistan? I can ask my friend, who lives in the US, to purchase the card for me and send me the code. I really need to make sure this will work before I spend $700 on a Lumia 1020.

Thanks in advance.

 

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And if I can't use a gift card from USA on an Australian account, can someone point me to where I can get one for Australia? I've searched everywhere but all I can find are USA based gift cards.