Due to the nature of how our payment provider (Stripe) works, you can only change your currency whilst not on a subscription/trial.
Log into your account on the Aitum website login.
(if you're already logged in, this link will redirect you to the Aitum homepage)
Click your username on the top right of the screen.
This will take you to the account page.
Under the Subscription section, click |manage".
This will take you to the our payment provider's portal.
On the right hand side - click the "Cancel plan" button.
Once your subscription has ran out, the currency selection dropdown will unlock on the Aitum website (pictured in step 2).
You can freely change your currency at this point.