It's possible that, when you were looking at your account page intending to renew, the country code at the top right of the page had inadvertently reset itself to default United States.
Customer Service are the best ones to ask about this. I've never bought a subscription myself as my ISP's have always offered it free, so I'm not able to tell you one way or the other, but I agree
account currencies should be clearly displayed.
Best call them, it's a free call and they will gladly refund any overcharge, if any.
Discussion moved to "My Account Online"