Hi @Michalis - welcome to the Community!
You can learn how to access your invoices here: https://support.atlassian.com/trello/docs/invoices-and-receipts-for-your-trello-subscription/
If you run into any issues with this, you will need to raise a ticket as we do not support billing issues over the Community. You can do this at https://trello.com/contact
If you do raise a ticket, please make sure you set the field What can we help you with? to 'Billing'.
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