Mailfence is based in Europe and bills in Euros €. If you are using a different currency in your country and you want to be billed with it. Then, no worries your credit card company will automatically convert the amount in your currency and will deduct the appropriate amount. To upgrade to a higher subscription please follow the steps in the KB article.
Are you having problems with billing-related queries? Then send us an email at support[at]mailfence.com