The currency on the players account is pre-set as per your country of residence and can not be changed.
This means that if you are a resident in the UK for example, the currency on your account will be in GBP (£), or if you are resident in Finland for example, the account currency will be in euro (€).
If you have moved to a new country and need your currency updating, please contact our customer support and we may have to make some changed to your account, however we will happily walk you through it.