Your invoice currency is usually set on your account when it's created, and it generally stays the same for consistency across your services. You can view which currency your invoices use in your client area under Billing > My Invoices.
If you need to switch to a different supported currency, this typically can't be changed by a simple self-service toggle, because existing invoices and services are tied to the original currency. The best approach is to open a ticket in billing, tell us your account and the currency you'd like to use, and we'll advise whether a change is possible for your account and how it affects current services and invoices.
