It is to be noted that the currency/language of the invoices can't be changed for an active Ahrefs subscription. 

To get invoices in a different currency or a different language of the invoices you will need to stop the current subscription and start a new one. 

To get assistance with setting up a new subscription with a different currency/language of the invoices, feel free to contact our support team via support@ahrefs.com or live chat.